diff --git a/src/CommunityToolkit.Diagnostics/Guard.String.cs b/src/CommunityToolkit.Diagnostics/Guard.String.cs
index 8b11eb6e3..e0b9419de 100644
--- a/src/CommunityToolkit.Diagnostics/Guard.String.cs
+++ b/src/CommunityToolkit.Diagnostics/Guard.String.cs
@@ -49,11 +49,11 @@ public static void IsNotNullOrEmpty([NotNull] string? text, [CallerArgumentExpre
     }
 
     /// <summary>
-    /// Asserts that the input <see cref="string"/> instance must be <see langword="null"/> or whitespace.
+    /// Asserts that the input <see cref="string"/> instance must be <see langword="null"/>, empty or consists only of white-space characters.
     /// </summary>
     /// <param name="text">The input <see cref="string"/> instance to test.</param>
     /// <param name="name">The name of the input parameter being tested.</param>
-    /// <exception cref="ArgumentException">Thrown if <paramref name="text"/> is neither <see langword="null"/> nor whitespace.</exception>
+    /// <exception cref="ArgumentException">Thrown if <paramref name="text"/> is neither <see langword="null"/>, nor empty, nor whitespace.</exception>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static void IsNullOrWhiteSpace(string? text, [CallerArgumentExpression(nameof(text))] string name = "")
     {
@@ -66,12 +66,12 @@ public static void IsNullOrWhiteSpace(string? text, [CallerArgumentExpression(na
     }
 
     /// <summary>
-    /// Asserts that the input <see cref="string"/> instance must not be <see langword="null"/> or whitespace.
+    /// Asserts that the input <see cref="string"/> instance must not be <see langword="null"/>, empty or consists only of white-space characters.
     /// </summary>
     /// <param name="text">The input <see cref="string"/> instance to test.</param>
     /// <param name="name">The name of the input parameter being tested.</param>
     /// <exception cref="ArgumentNullException">Thrown if <paramref name="text"/> is <see langword="null"/>.</exception>
-    /// <exception cref="ArgumentException">Thrown if <paramref name="text"/> is whitespace.</exception>
+    /// <exception cref="ArgumentException">Thrown if <paramref name="text"/> is empty or whitespace.</exception>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static void IsNotNullOrWhiteSpace([NotNull] string? text, [CallerArgumentExpression(nameof(text))] string name = "")
     {
@@ -118,15 +118,15 @@ public static void IsNotEmpty(string text, [CallerArgumentExpression(nameof(text
     }
 
     /// <summary>
-    /// Asserts that the input <see cref="string"/> instance must be whitespace.
+    /// Asserts that the input <see cref="string"/> instance must consists only of white-space characters.
     /// </summary>
     /// <param name="text">The input <see cref="string"/> instance to test.</param>
     /// <param name="name">The name of the input parameter being tested.</param>
-    /// <exception cref="ArgumentException">Thrown if <paramref name="text"/> is neither <see langword="null"/> nor whitespace.</exception>
+    /// <exception cref="ArgumentException">Thrown if <paramref name="text"/> has some not white-space characters.</exception>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static void IsWhiteSpace(string text, [CallerArgumentExpression(nameof(text))] string name = "")
     {
-        if (string.IsNullOrWhiteSpace(text))
+        if (!string.IsNullOrEmpty(text) && string.IsNullOrWhiteSpace(text))
         {
             return;
         }
@@ -135,15 +135,15 @@ public static void IsWhiteSpace(string text, [CallerArgumentExpression(nameof(te
     }
 
     /// <summary>
-    /// Asserts that the input <see cref="string"/> instance must not be <see langword="null"/> or whitespace.
+    /// Asserts that the input <see cref="string"/> instance must not consists only of white-space characters.
     /// </summary>
     /// <param name="text">The input <see cref="string"/> instance to test.</param>
     /// <param name="name">The name of the input parameter being tested.</param>
-    /// <exception cref="ArgumentException">Thrown if <paramref name="text"/> is <see langword="null"/> or whitespace.</exception>
+    /// <exception cref="ArgumentException">Thrown if <paramref name="text"/> has only white-space characters.</exception>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static void IsNotWhiteSpace(string text, [CallerArgumentExpression(nameof(text))] string name = "")
     {
-        if (!string.IsNullOrWhiteSpace(text))
+        if (string.IsNullOrEmpty(text) || !string.IsNullOrWhiteSpace(text))
         {
             return;
         }
diff --git a/src/CommunityToolkit.Diagnostics/Internals/Guard.String.ThrowHelper.cs b/src/CommunityToolkit.Diagnostics/Internals/Guard.String.ThrowHelper.cs
index 7c8818069..70d1bb17f 100644
--- a/src/CommunityToolkit.Diagnostics/Internals/Guard.String.ThrowHelper.cs
+++ b/src/CommunityToolkit.Diagnostics/Internals/Guard.String.ThrowHelper.cs
@@ -94,7 +94,7 @@ public static void ThrowArgumentExceptionForIsNotEmpty(string name)
         /// Throws an <see cref="ArgumentException"/> when <see cref="IsWhiteSpace"/> fails.
         /// </summary>
         [DoesNotReturn]
-        public static void ThrowArgumentExceptionForIsWhiteSpace(string text, string name)
+        public static void ThrowArgumentExceptionForIsWhiteSpace(string? text, string name)
         {
             throw new ArgumentException($"Parameter {AssertString(name)} (string) must be whitespace, was {AssertString(text)}.", name);
         }
@@ -103,7 +103,7 @@ public static void ThrowArgumentExceptionForIsWhiteSpace(string text, string nam
         /// Throws an <see cref="ArgumentException"/> when <see cref="IsNotWhiteSpace"/> fails.
         /// </summary>
         [DoesNotReturn]
-        public static void ThrowArgumentExceptionForIsNotWhiteSpace(string text, string name)
+        public static void ThrowArgumentExceptionForIsNotWhiteSpace(string? text, string name)
         {
             throw new ArgumentException($"Parameter {AssertString(name)} (string) must not be whitespace, was {AssertString(text)}.", name);
         }
diff --git a/tests/CommunityToolkit.Diagnostics.UnitTests/Test_Guard.cs b/tests/CommunityToolkit.Diagnostics.UnitTests/Test_Guard.cs
index 482df6fe8..0b225aba0 100644
--- a/tests/CommunityToolkit.Diagnostics.UnitTests/Test_Guard.cs
+++ b/tests/CommunityToolkit.Diagnostics.UnitTests/Test_Guard.cs
@@ -224,6 +224,50 @@ public void Test_Guard_IsNotNullOrWhiteSpace_Empty()
     {
         Guard.IsNotNullOrWhiteSpace("  ", nameof(Test_Guard_IsNotNullOrWhiteSpace_Empty));
     }
+    
+    [TestMethod]
+    public void Test_Guard_IsWhiteSpace_Ok()
+    {
+        Guard.IsWhiteSpace("  ", nameof(Test_Guard_IsWhiteSpace_Ok));
+        Guard.IsWhiteSpace("\t", nameof(Test_Guard_IsWhiteSpace_Ok));
+    }
+
+    [TestMethod]
+    [ExpectedException(typeof(ArgumentException))]
+    public void Test_Guard_IsWhiteSpace_Null()
+    {
+        Guard.IsWhiteSpace(null, nameof(Test_Guard_IsWhiteSpace_Null));
+    }
+    
+    [TestMethod]
+    [ExpectedException(typeof(ArgumentException))]
+    public void Test_Guard_IsWhiteSpace_Empty()
+    {
+        Guard.IsWhiteSpace(string.Empty, nameof(Test_Guard_IsWhiteSpace_Empty));
+    }
+
+    [TestMethod]
+    [ExpectedException(typeof(ArgumentException))]
+    public void Test_Guard_IsWhiteSpace_NotWhiteSpace()
+    {
+        Guard.IsWhiteSpace("foo", nameof(Test_Guard_IsWhiteSpace_NotWhiteSpace));
+    }
+    
+    [TestMethod]
+    public void Test_Guard_IsNotWhiteSpace_Ok()
+    {
+        Guard.IsNotWhiteSpace(null, nameof(Test_Guard_IsNotWhiteSpace_Ok));
+        Guard.IsNotWhiteSpace("foo", nameof(Test_Guard_IsNotWhiteSpace_Ok));
+        Guard.IsNotWhiteSpace(string.Empty, nameof(Test_Guard_IsNotWhiteSpace_Ok));
+    }
+
+    [TestMethod]
+    [ExpectedException(typeof(ArgumentException))]
+    public void Test_Guard_IsNotWhiteSpace_WhiteSpace()
+    {
+        Guard.IsNotWhiteSpace("  ", nameof(Test_Guard_IsNotWhiteSpace_WhiteSpace));
+        Guard.IsNotWhiteSpace("\t", nameof(Test_Guard_IsNotWhiteSpace_WhiteSpace));
+    }
 
     [TestMethod]
     public void Test_Guard_IsEqualTo_Ok()