diff --git a/src/libraries/System.Collections.Concurrent/src/Resources/Strings.resx b/src/libraries/System.Collections.Concurrent/src/Resources/Strings.resx
index 5edafe5a5db987..b15258417a5b23 100644
--- a/src/libraries/System.Collections.Concurrent/src/Resources/Strings.resx
+++ b/src/libraries/System.Collections.Concurrent/src/Resources/Strings.resx
@@ -126,6 +126,9 @@
   <data name="ConcurrentDictionary_KeyAlreadyExisted" xml:space="preserve">
     <value>The key already existed in the dictionary.</value>
   </data>
+  <data name="ConcurrentDictionary_ItemKeyIsNull" xml:space="preserve">
+    <value>TKey is a reference type and item.Key is null.</value>
+  </data>
   <data name="ConcurrentDictionary_TypeOfKeyIncorrect" xml:space="preserve">
     <value>The key was of an incorrect type for this dictionary.</value>
   </data>
diff --git a/src/libraries/System.Collections.Concurrent/src/System/Collections/Concurrent/ConcurrentDictionary.cs b/src/libraries/System.Collections.Concurrent/src/System/Collections/Concurrent/ConcurrentDictionary.cs
index 8a7afaede743f2..5748725a154a31 100644
--- a/src/libraries/System.Collections.Concurrent/src/System/Collections/Concurrent/ConcurrentDictionary.cs
+++ b/src/libraries/System.Collections.Concurrent/src/System/Collections/Concurrent/ConcurrentDictionary.cs
@@ -329,7 +329,10 @@ private void InitializeFromCollection(IEnumerable<KeyValuePair<TKey, TValue>> co
         {
             foreach (KeyValuePair<TKey, TValue> pair in collection)
             {
-                ArgumentNullException.ThrowIfNull(pair.Key, "key");
+                if (pair.Key is null)
+                {
+                    ThrowHelper.ThrowKeyNullException();
+                }
 
                 if (!TryAddInternal(_tables, pair.Key, null, pair.Value, updateIfExists: false, acquireLock: false, out _))
                 {
@@ -357,7 +360,10 @@ private void InitializeFromCollection(IEnumerable<KeyValuePair<TKey, TValue>> co
         /// <exception cref="OverflowException">The <see cref="ConcurrentDictionary{TKey, TValue}"/> contains too many elements.</exception>
         public bool TryAdd(TKey key, TValue value)
         {
-            ArgumentNullException.ThrowIfNull(key);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
 
             return TryAddInternal(_tables, key, null, value, updateIfExists: false, acquireLock: true, out _);
         }
@@ -383,7 +389,10 @@ public bool TryAdd(TKey key, TValue value)
         /// <exception cref="ArgumentNullException"><paramref name="key"/> is a null reference (Nothing in Visual Basic).</exception>
         public bool TryRemove(TKey key, [MaybeNullWhen(false)] out TValue value)
         {
-            ArgumentNullException.ThrowIfNull(key);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
 
             return TryRemoveInternal(key, out value, matchValue: false, default);
         }
@@ -405,7 +414,10 @@ public bool TryRemove(TKey key, [MaybeNullWhen(false)] out TValue value)
         /// </exception>
         public bool TryRemove(KeyValuePair<TKey, TValue> item)
         {
-            ArgumentNullException.ThrowIfNull(item.Key);
+            if (item.Key is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(item), SR.ConcurrentDictionary_ItemKeyIsNull);
+            }
 
             return TryRemoveInternal(item.Key, out _, matchValue: true, item.Value);
         }
@@ -503,7 +515,10 @@ private bool TryRemoveInternal(TKey key, [MaybeNullWhen(false)] out TValue value
         /// <exception cref="ArgumentNullException"><paramref name="key"/> is a null reference (Nothing in Visual Basic).</exception>
         public bool TryGetValue(TKey key, [MaybeNullWhen(false)] out TValue value)
         {
-            ArgumentNullException.ThrowIfNull(key);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
 
             Tables tables = _tables;
 
@@ -589,7 +604,10 @@ private static bool TryGetValueInternal(Tables tables, TKey key, int hashcode, [
         /// <exception cref="ArgumentNullException"><paramref name="key"/> is a null reference.</exception>
         public bool TryUpdate(TKey key, TValue newValue, TValue comparisonValue)
         {
-            ArgumentNullException.ThrowIfNull(key);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
 
             return TryUpdateInternal(_tables, key, null, newValue, comparisonValue);
         }
@@ -1080,7 +1098,10 @@ public TValue this[TKey key]
             }
             set
             {
-                ArgumentNullException.ThrowIfNull(key);
+                if (key is null)
+                {
+                    ThrowHelper.ThrowKeyNullException();
+                }
 
                 TryAddInternal(_tables, key, null, value, updateIfExists: true, acquireLock: true, out _);
             }
@@ -1184,8 +1205,15 @@ private int GetCountNoLocks()
         /// if the key was not in the dictionary.</returns>
         public TValue GetOrAdd(TKey key, Func<TKey, TValue> valueFactory)
         {
-            ArgumentNullException.ThrowIfNull(key);
-            ArgumentNullException.ThrowIfNull(valueFactory);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
+
+            if (valueFactory is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(valueFactory));
+            }
 
             Tables tables = _tables;
 
@@ -1219,8 +1247,15 @@ public TValue GetOrAdd(TKey key, Func<TKey, TValue> valueFactory)
         public TValue GetOrAdd<TArg>(TKey key, Func<TKey, TArg, TValue> valueFactory, TArg factoryArgument)
             where TArg : allows ref struct
         {
-            ArgumentNullException.ThrowIfNull(key);
-            ArgumentNullException.ThrowIfNull(valueFactory);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
+
+            if (valueFactory is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(valueFactory));
+            }
 
             Tables tables = _tables;
 
@@ -1249,7 +1284,10 @@ public TValue GetOrAdd<TArg>(TKey key, Func<TKey, TArg, TValue> valueFactory, TA
         /// key is already in the dictionary, or the new value if the key was not in the dictionary.</returns>
         public TValue GetOrAdd(TKey key, TValue value)
         {
-            ArgumentNullException.ThrowIfNull(key);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
 
             Tables tables = _tables;
 
@@ -1288,9 +1326,20 @@ public TValue AddOrUpdate<TArg>(
             TKey key, Func<TKey, TArg, TValue> addValueFactory, Func<TKey, TValue, TArg, TValue> updateValueFactory, TArg factoryArgument)
             where TArg : allows ref struct
         {
-            ArgumentNullException.ThrowIfNull(key);
-            ArgumentNullException.ThrowIfNull(addValueFactory);
-            ArgumentNullException.ThrowIfNull(updateValueFactory);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
+
+            if (addValueFactory is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(addValueFactory));
+            }
+
+            if (updateValueFactory is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(updateValueFactory));
+            }
 
             Tables tables = _tables;
 
@@ -1350,9 +1399,20 @@ public TValue AddOrUpdate<TArg>(
         /// absent) or the result of updateValueFactory (if the key was present).</returns>
         public TValue AddOrUpdate(TKey key, Func<TKey, TValue> addValueFactory, Func<TKey, TValue, TValue> updateValueFactory)
         {
-            ArgumentNullException.ThrowIfNull(key);
-            ArgumentNullException.ThrowIfNull(addValueFactory);
-            ArgumentNullException.ThrowIfNull(updateValueFactory);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
+
+            if (addValueFactory is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(addValueFactory));
+            }
+
+            if (updateValueFactory is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(updateValueFactory));
+            }
 
             Tables tables = _tables;
 
@@ -1410,8 +1470,15 @@ public TValue AddOrUpdate(TKey key, Func<TKey, TValue> addValueFactory, Func<TKe
         /// absent) or the result of updateValueFactory (if the key was present).</returns>
         public TValue AddOrUpdate(TKey key, TValue addValue, Func<TKey, TValue, TValue> updateValueFactory)
         {
-            ArgumentNullException.ThrowIfNull(key);
-            ArgumentNullException.ThrowIfNull(updateValueFactory);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
+
+            if (updateValueFactory is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(updateValueFactory));
+            }
 
             Tables tables = _tables;
 
@@ -1632,7 +1699,11 @@ bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> k
         /// </exception>
         void IDictionary.Add(object key, object? value)
         {
-            ArgumentNullException.ThrowIfNull(key);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
+
             if (!(key is TKey))
             {
                 throw new ArgumentException(SR.ConcurrentDictionary_TypeOfKeyIncorrect);
@@ -1655,7 +1726,10 @@ void IDictionary.Add(object key, object? value)
         /// (Nothing in Visual Basic).</exception>
         bool IDictionary.Contains(object key)
         {
-            ArgumentNullException.ThrowIfNull(key);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
 
             return key is TKey tkey && ContainsKey(tkey);
         }
@@ -1703,7 +1777,10 @@ bool IDictionary.Contains(object key)
         /// (Nothing in Visual Basic).</exception>
         void IDictionary.Remove(object key)
         {
-            ArgumentNullException.ThrowIfNull(key);
+            if (key is null)
+            {
+                ThrowHelper.ThrowKeyNullException();
+            }
 
             if (key is TKey tkey)
             {
@@ -1741,7 +1818,10 @@ void IDictionary.Remove(object key)
         {
             get
             {
-                ArgumentNullException.ThrowIfNull(key);
+                if (key is null)
+                {
+                    ThrowHelper.ThrowKeyNullException();
+                }
 
                 if (key is TKey tkey && TryGetValue(tkey, out TValue? value))
                 {
@@ -1752,7 +1832,10 @@ void IDictionary.Remove(object key)
             }
             set
             {
-                ArgumentNullException.ThrowIfNull(key);
+                if (key is null)
+                {
+                    ThrowHelper.ThrowKeyNullException();
+                }
 
                 if (!(key is TKey))
                 {
@@ -2408,7 +2491,10 @@ private bool TryAdd(TAlternateKey key, TValue value, bool updateIfExists, out TV
                         }
 
                         TKey actualKey = comparer.Create(key);
-                        ArgumentNullException.ThrowIfNull(actualKey, nameof(key));
+                        if (actualKey is null)
+                        {
+                            ThrowHelper.ThrowKeyNullException();
+                        }
 
                         // The key was not found in the bucket. Insert the key-value pair.
                         var resultNode = new Node(actualKey, value, hashcode, bucket);
@@ -2638,7 +2724,10 @@ internal sealed class IDictionaryDebugView<TKey, TValue> where TKey : notnull
 
         public IDictionaryDebugView(IDictionary<TKey, TValue> dictionary)
         {
-            ArgumentNullException.ThrowIfNull(dictionary);
+            if (dictionary is null)
+            {
+                ThrowHelper.ThrowArgumentNullException(nameof(dictionary));
+            }
 
             _dictionary = dictionary;
         }
diff --git a/src/libraries/System.Collections.Concurrent/src/System/ThrowHelper.cs b/src/libraries/System.Collections.Concurrent/src/System/ThrowHelper.cs
index ea06bf6a3c307f..bb8a35bac4e414 100644
--- a/src/libraries/System.Collections.Concurrent/src/System/ThrowHelper.cs
+++ b/src/libraries/System.Collections.Concurrent/src/System/ThrowHelper.cs
@@ -8,7 +8,13 @@ namespace System
     internal static class ThrowHelper
     {
         [DoesNotReturn]
-        internal static void ThrowKeyNullException() => throw new ArgumentNullException("key");
+        internal static void ThrowKeyNullException() => ThrowArgumentNullException("key");
+
+        [DoesNotReturn]
+        internal static void ThrowArgumentNullException(string name) => throw new ArgumentNullException(name);
+
+        [DoesNotReturn]
+        internal static void ThrowArgumentNullException(string name, string message) => throw new ArgumentNullException(name, message);
 
         [DoesNotReturn]
         internal static void ThrowValueNullException() => throw new ArgumentException(SR.ConcurrentDictionary_TypeOfValueIncorrect);
diff --git a/src/libraries/System.Collections.Concurrent/tests/ConcurrentDictionary/ConcurrentDictionaryTests.cs b/src/libraries/System.Collections.Concurrent/tests/ConcurrentDictionary/ConcurrentDictionaryTests.cs
index 500d8b88f9dccf..c92689a6b034f4 100644
--- a/src/libraries/System.Collections.Concurrent/tests/ConcurrentDictionary/ConcurrentDictionaryTests.cs
+++ b/src/libraries/System.Collections.Concurrent/tests/ConcurrentDictionary/ConcurrentDictionaryTests.cs
@@ -449,7 +449,7 @@ public static void TestRemove3()
         [Fact]
         public static void TryRemove_KeyValuePair_ArgumentValidation()
         {
-            AssertExtensions.Throws<ArgumentNullException>("item.Key", () => new ConcurrentDictionary<string, int>().TryRemove(new KeyValuePair<string, int>(null, 42)));
+            AssertExtensions.Throws<ArgumentNullException>("item", () => new ConcurrentDictionary<string, int>().TryRemove(new KeyValuePair<string, int>(null, 42)));
             new ConcurrentDictionary<int, int>().TryRemove(new KeyValuePair<int, int>(0, 0)); // no error when using default value type
             new ConcurrentDictionary<int?, int>().TryRemove(new KeyValuePair<int?, int>(0, 0)); // or nullable
         }