diff --git a/src/OptionalValues/Extensions/DictionaryExtensions.cs b/src/OptionalValues/Extensions/DictionaryExtensions.cs
new file mode 100644
index 0000000..2998852
--- /dev/null
+++ b/src/OptionalValues/Extensions/DictionaryExtensions.cs
@@ -0,0 +1,64 @@
+namespace OptionalValues.Extensions;
+
+/// <summary>
+/// Extension methods for <see cref="IDictionary{TKey, TValue}"/>.
+/// </summary>
+public static class DictionaryExtensions
+{
+    /// <summary>
+    /// Gets the value associated with the specified key, returning <see cref="OptionalValue{T}.Unspecified"/> if the key is not found.
+    /// </summary>
+    /// <returns>A specified <see cref="OptionalValue{T}"/> when the key is found, or an <see cref="OptionalValue{T}.Unspecified"/> when the key is not found.</returns>
+    public static OptionalValue<T> GetOptionalValue<TKey, T>(this IDictionary<TKey, T> dictionary, TKey key)
+    {
+        ArgumentNullException.ThrowIfNull(dictionary);
+        ArgumentNullException.ThrowIfNull(key);
+
+        return dictionary.TryGetValue(key, out T? value) ? new OptionalValue<T>(value) : OptionalValue<T>.Unspecified;
+    }
+
+    /// <summary>
+    /// Adds the specified key and value to the dictionary if the value is specified.
+    /// </summary>
+    /// <exception cref="ArgumentException">When value is specified and the key already exists in the dictionary.</exception>
+    /// <exception cref="ArgumentNullException">The key is null.</exception>
+    public static void AddOptionalValue<TKey, T>(this IDictionary<TKey, T> dictionary, TKey key, OptionalValue<T> value)
+    {
+        ArgumentNullException.ThrowIfNull(dictionary);
+        ArgumentNullException.ThrowIfNull(key);
+
+        if (value.IsSpecified)
+        {
+            dictionary.Add(key, value.SpecifiedValue);
+        }
+    }
+
+    /// <summary>
+    /// Adds the specified key and value to the dictionary if the value is specified.
+    /// </summary>
+    /// <exception cref="ArgumentException">When value is specified and the key already exists in the dictionary.</exception>
+    /// <exception cref="ArgumentNullException">The key is null.</exception>
+    /// <returns><see langword="true"/> if the value was added to the dictionary; otherwise when the <paramref name="key"/> already exists or the value is <see cref="OptionalValue{T}.Unspecified"/>, <see langword="false"/>.</returns>
+    public static bool TryAddOptionalValue<TKey, T>(this IDictionary<TKey, T> dictionary, TKey key, OptionalValue<T> value)
+    {
+        ArgumentNullException.ThrowIfNull(dictionary);
+        ArgumentNullException.ThrowIfNull(key);
+
+        return value.IsSpecified && dictionary.TryAdd(key, value.SpecifiedValue);
+    }
+
+    /// <summary>
+    /// Sets the specified key and value in the dictionary if the value is specified.
+    /// </summary>
+    /// <exception cref="ArgumentNullException">The key is null.</exception>
+    public static void SetOptionalValue<TKey, T>(this IDictionary<TKey, T> dictionary, TKey key, OptionalValue<T> value)
+    {
+        ArgumentNullException.ThrowIfNull(dictionary);
+        ArgumentNullException.ThrowIfNull(key);
+
+        if (value.IsSpecified)
+        {
+            dictionary[key] = value.SpecifiedValue;
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/OptionalValues/PublicAPI.Unshipped.txt b/src/OptionalValues/PublicAPI.Unshipped.txt
index 6459d04..aa77a42 100644
--- a/src/OptionalValues/PublicAPI.Unshipped.txt
+++ b/src/OptionalValues/PublicAPI.Unshipped.txt
@@ -1,6 +1,11 @@
+OptionalValues.Extensions.DictionaryExtensions
 OptionalValues.OptionalValueJsonConverterAttribute
 OptionalValues.OptionalValueJsonConverterAttribute.InnerConverterType.get -> System.Type?
 OptionalValues.OptionalValueJsonConverterAttribute.OptionalValueJsonConverterAttribute() -> void
 OptionalValues.OptionalValueJsonConverterAttribute.OptionalValueJsonConverterAttribute(System.Type! innerConverterType) -> void
 override OptionalValues.OptionalValueJsonConverterAttribute.CreateConverter(System.Type! typeToConvert) -> System.Text.Json.Serialization.JsonConverter?
+static OptionalValues.Extensions.DictionaryExtensions.AddOptionalValue<TKey, T>(this System.Collections.Generic.IDictionary<TKey, T>! dictionary, TKey key, OptionalValues.OptionalValue<T> value) -> void
+static OptionalValues.Extensions.DictionaryExtensions.GetOptionalValue<TKey, T>(this System.Collections.Generic.IDictionary<TKey, T>! dictionary, TKey key) -> OptionalValues.OptionalValue<T>
+static OptionalValues.Extensions.DictionaryExtensions.SetOptionalValue<TKey, T>(this System.Collections.Generic.IDictionary<TKey, T>! dictionary, TKey key, OptionalValues.OptionalValue<T> value) -> void
+static OptionalValues.Extensions.DictionaryExtensions.TryAddOptionalValue<TKey, T>(this System.Collections.Generic.IDictionary<TKey, T>! dictionary, TKey key, OptionalValues.OptionalValue<T> value) -> bool
 virtual OptionalValues.OptionalValueJsonConverterAttribute.CreateInnerConverter() -> System.Text.Json.Serialization.JsonConverter!
\ No newline at end of file
diff --git a/test/OptionalValues.Tests/Extensions/DictionaryExtensionsTest.cs b/test/OptionalValues.Tests/Extensions/DictionaryExtensionsTest.cs
new file mode 100644
index 0000000..1b2a314
--- /dev/null
+++ b/test/OptionalValues.Tests/Extensions/DictionaryExtensionsTest.cs
@@ -0,0 +1,295 @@
+using OptionalValues.Extensions;
+
+namespace OptionalValues.Tests.Extensions;
+
+public class DictionaryExtensionsTest
+{
+    public class GetOptionalValue : DictionaryExtensionsTest
+    {
+        [Fact]
+        public void ReturnsUnspecifiedWhenKeyIsNotFound()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>();
+
+            // Act
+            OptionalValue<int> result = dictionary.GetOptionalValue("key");
+
+            // Assert
+            Assert.False(result.IsSpecified);
+        }
+
+        [Fact]
+        public void ReturnsSpecifiedValueWhenKeyIsFound()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>
+            {
+                ["key"] = 42
+            };
+
+            // Act
+            OptionalValue<int> result = dictionary.GetOptionalValue("key");
+
+            // Assert
+            Assert.True(result.IsSpecified);
+            Assert.Equal(42, result.SpecifiedValue);
+        }
+
+        [Fact]
+        public void ThrowsArgumentNullExceptionWhenDictionaryIsNull()
+        {
+            // Arrange
+            IDictionary<string, int> dictionary = null!;
+
+            // Act
+            Action action = () => dictionary.GetOptionalValue("key");
+
+            // Assert
+            ArgumentNullException exception = Assert.Throws<ArgumentNullException>(action);
+            Assert.Equal("dictionary", exception.ParamName);
+        }
+
+        [Fact]
+        public void ThrowsArgumentNullExceptionWhenKeyIsNull()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>();
+
+            // Act
+            Action action = () => dictionary.GetOptionalValue(null!);
+
+            // Assert
+            ArgumentNullException exception = Assert.Throws<ArgumentNullException>(action);
+            Assert.Equal("key", exception.ParamName);
+        }
+    }
+
+    public class AddOptionalValue : DictionaryExtensionsTest
+    {
+        [Fact]
+        public void AddsValueWhenSpecified()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>();
+
+            // Act
+            dictionary.AddOptionalValue("key", new OptionalValue<int>(42));
+
+            // Assert
+            Assert.Equal(42, dictionary["key"]);
+        }
+
+        [Fact]
+        public void DoesNotAddValueWhenUnspecified()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>();
+
+            // Act
+            dictionary.AddOptionalValue("key", OptionalValue<int>.Unspecified);
+
+            // Assert
+            Assert.Empty(dictionary);
+        }
+
+        [Fact]
+        public void ThrowsArgumentNullExceptionWhenDictionaryIsNull()
+        {
+            // Arrange
+            IDictionary<string, int> dictionary = null!;
+
+            // Act
+            Action action = () => dictionary.AddOptionalValue("key", new OptionalValue<int>(42));
+
+            // Assert
+            ArgumentNullException exception = Assert.Throws<ArgumentNullException>(action);
+            Assert.Equal("dictionary", exception.ParamName);
+        }
+
+        [Fact]
+        public void ThrowsArgumentNullExceptionWhenKeyIsNull()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>();
+
+            // Act
+            Action action = () => dictionary.AddOptionalValue(null!, new OptionalValue<int>(42));
+
+            // Assert
+            ArgumentNullException exception = Assert.Throws<ArgumentNullException>(action);
+            Assert.Equal("key", exception.ParamName);
+        }
+
+        [Fact]
+        public void ThrowsArgumentExceptionWhenKeyAlreadyExists()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>
+            {
+                ["key"] = 42
+            };
+
+            // Act
+            Action action = () => dictionary.AddOptionalValue("key", new OptionalValue<int>(42));
+
+            // Assert
+            Assert.Throws<ArgumentException>(action);
+        }
+    }
+
+    public class TryAddOptionalValue : DictionaryExtensionsTest
+    {
+        [Fact]
+        public void AddsValueWhenSpecified()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>();
+
+            // Act
+            var result = dictionary.TryAddOptionalValue("key", new OptionalValue<int>(42));
+
+            // Assert
+            Assert.True(result);
+            Assert.Equal(42, dictionary["key"]);
+        }
+
+        [Fact]
+        public void DoesNotAddValueWhenUnspecified()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>();
+
+            // Act
+            var result = dictionary.TryAddOptionalValue("key", OptionalValue<int>.Unspecified);
+
+            // Assert
+            Assert.False(result);
+            Assert.Empty(dictionary);
+        }
+
+        [Fact]
+        public void DoesNotAddWhenKeyExists()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>
+            {
+                ["key"] = 42
+            };
+
+            // Act
+            var result = dictionary.TryAddOptionalValue("key", new OptionalValue<int>(9000));
+
+            // Assert
+            Assert.False(result);
+            Assert.Equal(42, dictionary["key"]);
+        }
+
+        [Fact]
+        public void ThrowsArgumentNullExceptionWhenDictionaryIsNull()
+        {
+            // Arrange
+            IDictionary<string, int> dictionary = null!;
+
+            // Act
+            Action action = () => dictionary.TryAddOptionalValue("key", new OptionalValue<int>(42));
+
+            // Assert
+            ArgumentNullException exception = Assert.Throws<ArgumentNullException>(action);
+            Assert.Equal("dictionary", exception.ParamName);
+        }
+
+        [Fact]
+        public void ThrowsArgumentNullExceptionWhenKeyIsNull()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>();
+
+            // Act
+            Action action = () => dictionary.TryAddOptionalValue(null!, new OptionalValue<int>(42));
+
+            // Assert
+            ArgumentNullException exception = Assert.Throws<ArgumentNullException>(action);
+            Assert.Equal("key", exception.ParamName);
+        }
+    }
+
+    public class SetOptionalValue : DictionaryExtensionsTest
+    {
+        [Fact]
+        public void SetsValueWhenSpecified()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>
+            {
+                ["key"] = 42
+            };
+
+            // Act
+            dictionary.SetOptionalValue("key", new OptionalValue<int>(9000));
+
+            // Assert
+            Assert.Equal(9000, dictionary["key"]);
+        }
+
+        [Fact]
+        public void DoesNotSetValueWhenUnspecified()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>
+            {
+                ["key"] = 42
+            };
+
+            // Act
+            dictionary.SetOptionalValue("key", OptionalValue<int>.Unspecified);
+
+            // Assert
+            Assert.Equal(42, dictionary["key"]);
+        }
+
+        [Fact]
+        public void OverwritesValueWhenSpecified()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>
+            {
+                ["key"] = 42
+            };
+
+            // Act
+            dictionary.SetOptionalValue("key", new OptionalValue<int>(9000));
+
+            // Assert
+            Assert.Equal(9000, dictionary["key"]);
+        }
+
+        [Fact]
+        public void ThrowsArgumentNullExceptionWhenDictionaryIsNull()
+        {
+            // Arrange
+            IDictionary<string, int> dictionary = null!;
+
+            // Act
+            Action action = () => dictionary.SetOptionalValue("key", new OptionalValue<int>(42));
+
+            // Assert
+            ArgumentNullException exception = Assert.Throws<ArgumentNullException>(action);
+            Assert.Equal("dictionary", exception.ParamName);
+        }
+
+        [Fact]
+        public void ThrowsArgumentNullExceptionWhenKeyIsNull()
+        {
+            // Arrange
+            var dictionary = new Dictionary<string, int>();
+
+            // Act
+            Action action = () => dictionary.SetOptionalValue(null!, new OptionalValue<int>(42));
+
+            // Assert
+            ArgumentNullException exception = Assert.Throws<ArgumentNullException>(action);
+            Assert.Equal("key", exception.ParamName);
+        }
+    }
+}
\ No newline at end of file