diff --git a/src/libraries/System.Private.CoreLib/src/System/Threading/ManualResetEventSlim.cs b/src/libraries/System.Private.CoreLib/src/System/Threading/ManualResetEventSlim.cs
index b049a9aaeebeb..d4a77457b4a38 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Threading/ManualResetEventSlim.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Threading/ManualResetEventSlim.cs
@@ -344,9 +344,6 @@ public void Reset()
         /// The caller of this method blocks indefinitely until the current instance is set. The caller will
         /// return immediately if the event is currently in a set state.
         /// </remarks>
-#if !FEATURE_WASM_THREADS
-        [UnsupportedOSPlatform("browser")]
-#endif
         public void Wait()
         {
             Wait(Timeout.Infinite, CancellationToken.None);
@@ -367,9 +364,6 @@ public void Wait()
         /// The caller of this method blocks indefinitely until the current instance is set. The caller will
         /// return immediately if the event is currently in a set state.
         /// </remarks>
-#if !FEATURE_WASM_THREADS
-        [UnsupportedOSPlatform("browser")]
-#endif
         public void Wait(CancellationToken cancellationToken)
         {
             Wait(Timeout.Infinite, cancellationToken);
@@ -390,9 +384,6 @@ public void Wait(CancellationToken cancellationToken)
         /// <exception cref="InvalidOperationException">
         /// The maximum number of waiters has been exceeded.
         /// </exception>
-#if !FEATURE_WASM_THREADS
-        [UnsupportedOSPlatform("browser")]
-#endif
         public bool Wait(TimeSpan timeout)
         {
             long totalMilliseconds = (long)timeout.TotalMilliseconds;
@@ -423,9 +414,6 @@ public bool Wait(TimeSpan timeout)
         /// <exception cref="InvalidOperationException">
         /// The maximum number of waiters has been exceeded.
         /// </exception>
-#if !FEATURE_WASM_THREADS
-        [UnsupportedOSPlatform("browser")]
-#endif
         public bool Wait(TimeSpan timeout, CancellationToken cancellationToken)
         {
             long totalMilliseconds = (long)timeout.TotalMilliseconds;
@@ -449,9 +437,6 @@ public bool Wait(TimeSpan timeout, CancellationToken cancellationToken)
         /// <exception cref="InvalidOperationException">
         /// The maximum number of waiters has been exceeded.
         /// </exception>
-#if !FEATURE_WASM_THREADS
-        [UnsupportedOSPlatform("browser")]
-#endif
         public bool Wait(int millisecondsTimeout)
         {
             return Wait(millisecondsTimeout, CancellationToken.None);
@@ -475,9 +460,6 @@ public bool Wait(int millisecondsTimeout)
         /// </exception>
         /// <exception cref="OperationCanceledException"><paramref
         /// name="cancellationToken"/> was canceled.</exception>
-#if !FEATURE_WASM_THREADS
-        [UnsupportedOSPlatform("browser")]
-#endif
         public bool Wait(int millisecondsTimeout, CancellationToken cancellationToken)
         {
             ObjectDisposedException.ThrowIf(IsDisposed, this);
diff --git a/src/libraries/System.Private.CoreLib/src/System/Threading/Monitor.cs b/src/libraries/System.Private.CoreLib/src/System/Threading/Monitor.cs
index 8fe478a52dc9a..37939a7f043d2 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Threading/Monitor.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Threading/Monitor.cs
@@ -13,27 +13,15 @@ public static bool TryEnter(object obj, TimeSpan timeout)
         public static void TryEnter(object obj, TimeSpan timeout, ref bool lockTaken)
             => TryEnter(obj, WaitHandle.ToTimeoutMilliseconds(timeout), ref lockTaken);
 
-#if !FEATURE_WASM_THREADS
-        [UnsupportedOSPlatform("browser")]
-#endif
         public static bool Wait(object obj, TimeSpan timeout) => Wait(obj, WaitHandle.ToTimeoutMilliseconds(timeout));
 
-#if !FEATURE_WASM_THREADS
-        [UnsupportedOSPlatform("browser")]
-#endif
         public static bool Wait(object obj) => Wait(obj, Timeout.Infinite);
 
         // Remoting is not supported, exitContext argument is unused
-#if !FEATURE_WASM_THREADS
-        [UnsupportedOSPlatform("browser")]
-#endif
         public static bool Wait(object obj, int millisecondsTimeout, bool exitContext)
             => Wait(obj, millisecondsTimeout);
 
         // Remoting is not supported, exitContext argument is unused
-#if !FEATURE_WASM_THREADS
-        [UnsupportedOSPlatform("browser")]
-#endif
         public static bool Wait(object obj, TimeSpan timeout, bool exitContext)
             => Wait(obj, WaitHandle.ToTimeoutMilliseconds(timeout));
     }