diff --git a/Activout.RestClient.Test/DictionaryParameterTests.cs b/Activout.RestClient.Test/DictionaryParameterTests.cs
new file mode 100644
index 0000000..e215f58
--- /dev/null
+++ b/Activout.RestClient.Test/DictionaryParameterTests.cs
@@ -0,0 +1,197 @@
+using System.Collections.Generic;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
+using RichardSzalay.MockHttp;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Activout.RestClient.Test;
+
+public class DictionaryParameterTests(ITestOutputHelper outputHelper)
+{
+    private const string BaseUri = "https://example.com/api";
+    
+    private readonly IRestClientFactory _restClientFactory = Services.CreateRestClientFactory();
+    private readonly MockHttpMessageHandler _mockHttp = new MockHttpMessageHandler();
+    private readonly ILoggerFactory _loggerFactory = LoggerFactoryHelpers.CreateLoggerFactory(outputHelper);
+
+    private IRestClientBuilder CreateRestClientBuilder()
+    {
+        return _restClientFactory.CreateBuilder()
+            .With(_loggerFactory.CreateLogger<DictionaryParameterTests>())
+            .With(_mockHttp.ToHttpClient())
+            .BaseUri(BaseUri);
+    }
+
+    [Fact]
+    public async Task TestQueryParamDictionary()
+    {
+        // arrange
+        var service = CreateRestClientBuilder().Build<ITestService>();
+        var queryParams = new Dictionary<string, string>
+        {
+            ["param1"] = "value1",
+            ["param2"] = "value2"
+        };
+
+        _mockHttp
+            .When("https://example.com/api/test")
+            .WithQueryString("param1=value1&param2=value2")
+            .Respond("application/json", "{}");
+
+        // act
+        await service.TestQueryParamDictionary(queryParams);
+
+        // assert
+        _mockHttp.VerifyNoOutstandingExpectation();
+    }
+
+    [Fact]
+    public async Task TestFormParamDictionary()
+    {
+        // arrange
+        var service = CreateRestClientBuilder().Build<ITestService>();
+        var formParams = new Dictionary<string, string>
+        {
+            ["field1"] = "value1",
+            ["field2"] = "value2"
+        };
+
+        _mockHttp
+            .When(HttpMethod.Post, "https://example.com/api/test")
+            .WithFormData("field1", "value1")
+            .WithFormData("field2", "value2")
+            .Respond("application/json", "{}");
+
+        // act
+        await service.TestFormParamDictionary(formParams);
+
+        // assert
+        _mockHttp.VerifyNoOutstandingExpectation();
+    }
+
+    [Fact]
+    public async Task TestHeaderParamDictionary()
+    {
+        // arrange
+        var service = CreateRestClientBuilder().Build<ITestService>();
+        var headers = new Dictionary<string, string>
+        {
+            ["X-Custom-Header1"] = "value1",
+            ["X-Custom-Header2"] = "value2"
+        };
+
+        _mockHttp
+            .When("https://example.com/api/test")
+            .WithHeaders("X-Custom-Header1", "value1")
+            .WithHeaders("X-Custom-Header2", "value2")
+            .Respond("application/json", "{}");
+
+        // act
+        await service.TestHeaderParamDictionary(headers);
+
+        // assert
+        _mockHttp.VerifyNoOutstandingExpectation();
+    }
+
+    [Fact]
+    public async Task TestMixedDictionaryAndRegularParams()
+    {
+        // arrange
+        var service = CreateRestClientBuilder().Build<ITestService>();
+        var queryParams = new Dictionary<string, string>
+        {
+            ["param1"] = "value1",
+            ["param2"] = "value2"
+        };
+
+        _mockHttp
+            .When("https://example.com/api/test")
+            .WithQueryString("param1=value1&param2=value2&singleParam=singleValue")
+            .Respond("application/json", "{}");
+
+        // act
+        await service.TestMixedParams(queryParams, "singleValue");
+
+        // assert
+        _mockHttp.VerifyNoOutstandingExpectation();
+    }
+
+    [Fact]
+    public async Task TestEmptyDictionary()
+    {
+        // arrange
+        var service = CreateRestClientBuilder().Build<ITestService>();
+        var emptyParams = new Dictionary<string, string>();
+
+        _mockHttp
+            .When("https://example.com/api/test")
+            .Respond("application/json", "{}");
+
+        // act
+        await service.TestQueryParamDictionary(emptyParams);
+
+        // assert
+        _mockHttp.VerifyNoOutstandingExpectation();
+    }
+
+    [Fact]
+    public async Task TestNullDictionaryValues()
+    {
+        // arrange
+        var service = CreateRestClientBuilder().Build<ITestService>();
+        var paramsWithNull = new Dictionary<string, string>
+        {
+            ["param1"] = "value1",
+            ["param2"] = null
+        };
+
+        _mockHttp
+            .When("https://example.com/api/test")
+            .WithQueryString("param1=value1&param2=")
+            .Respond("application/json", "{}");
+
+        // act
+        await service.TestQueryParamDictionary(paramsWithNull);
+
+        // assert
+        _mockHttp.VerifyNoOutstandingExpectation();
+    }
+
+    [Fact]
+    public async Task TestBackwardCompatibilityWithNonDictionaryParams()
+    {
+        // arrange
+        var service = CreateRestClientBuilder().Build<ITestService>();
+
+        _mockHttp
+            .When("https://example.com/api/test")
+            .WithQueryString("regularParam=regularValue")
+            .Respond("application/json", "{}");
+
+        // act
+        await service.TestRegularParam("regularValue");
+
+        // assert
+        _mockHttp.VerifyNoOutstandingExpectation();
+    }
+}
+
+public interface ITestService
+{
+    [Get("test")]
+    Task TestQueryParamDictionary([QueryParam] Dictionary<string, string> queryParams);
+
+    [Post("test")]
+    Task TestFormParamDictionary([FormParam] Dictionary<string, string> formParams);
+
+    [Get("test")]
+    Task TestHeaderParamDictionary([HeaderParam] Dictionary<string, string> headers);
+
+    [Get("test")]
+    Task TestMixedParams([QueryParam] Dictionary<string, string> queryParams, [QueryParam("singleParam")] string singleParam);
+
+    [Get("test")]
+    Task TestRegularParam([QueryParam("regularParam")] string regularParam);
+}
\ No newline at end of file
diff --git a/Activout.RestClient/Implementation/RequestHandler.cs b/Activout.RestClient/Implementation/RequestHandler.cs
index 87ba7d3..1928913 100644
--- a/Activout.RestClient/Implementation/RequestHandler.cs
+++ b/Activout.RestClient/Implementation/RequestHandler.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using System.Net;
@@ -295,20 +296,56 @@ private CancellationToken GetParams(
                     }
                     else if (attribute is QueryParamAttribute queryParamAttribute)
                     {
-                        queryParams.Add(Uri.EscapeDataString(queryParamAttribute.Name ?? parameterName) + "=" +
-                                        Uri.EscapeDataString(stringValue));
+                        if (rawValue is IDictionary dictionary)
+                        {
+                            foreach (DictionaryEntry entry in dictionary)
+                            {
+                                var key = entry.Key?.ToString() ?? string.Empty;
+                                var value = entry.Value?.ToString() ?? string.Empty;
+                                queryParams.Add(Uri.EscapeDataString(key) + "=" + Uri.EscapeDataString(value));
+                            }
+                        }
+                        else
+                        {
+                            queryParams.Add(Uri.EscapeDataString(queryParamAttribute.Name ?? parameterName) + "=" +
+                                            Uri.EscapeDataString(stringValue));
+                        }
                         handled = true;
                     }
                     else if (attribute is FormParamAttribute formParamAttribute)
                     {
-                        formParams.Add(new KeyValuePair<string, string>(formParamAttribute.Name ?? parameterName,
-                            stringValue));
+                        if (rawValue is IDictionary dictionary)
+                        {
+                            foreach (DictionaryEntry entry in dictionary)
+                            {
+                                var key = entry.Key?.ToString() ?? string.Empty;
+                                var value = entry.Value?.ToString() ?? string.Empty;
+                                formParams.Add(new KeyValuePair<string, string>(key, value));
+                            }
+                        }
+                        else
+                        {
+                            formParams.Add(new KeyValuePair<string, string>(formParamAttribute.Name ?? parameterName,
+                                stringValue));
+                        }
                         handled = true;
                     }
                     else if (attribute is HeaderParamAttribute headerParamAttribute)
                     {
-                        headers.AddOrReplaceHeader(headerParamAttribute.Name ?? parameterName, stringValue,
-                            headerParamAttribute.Replace);
+                        if (rawValue is IDictionary dictionary)
+                        {
+                            foreach (DictionaryEntry entry in dictionary)
+                            {
+                                var key = entry.Key?.ToString() ?? string.Empty;
+                                var value = entry.Value?.ToString() ?? string.Empty;
+                                headers.AddOrReplaceHeader(key, value, headerParamAttribute.Replace);
+                            }
+                        }
+                        else
+                        {
+                            headers.AddOrReplaceHeader(headerParamAttribute.Name ?? parameterName, stringValue,
+                                headerParamAttribute.Replace);
+                        }
                         handled = true;
                     }
                 }