diff --git a/native/yaha_native/src/binding.rs b/native/yaha_native/src/binding.rs
index c03791d..b803c81 100644
--- a/native/yaha_native/src/binding.rs
+++ b/native/yaha_native/src/binding.rs
@@ -70,6 +70,34 @@ pub extern "C" fn yaha_client_config_add_root_certificates(ctx: *mut YahaNativeC
     valid
 }
 
+#[no_mangle]
+pub extern "C" fn yaha_client_config_add_client_auth_certificates(ctx: *mut YahaNativeContext, auth_certs: *const StringBuffer) -> usize {
+    let ctx = YahaNativeContextInternal::from_raw_context(ctx);
+    let certs: Vec<rustls::Certificate> = unsafe { rustls_pemfile::certs(&mut (*auth_certs).to_bytes()).unwrap().into_iter().map(rustls::Certificate).collect() };
+
+    let count = certs.len();
+
+    if count > 0 {
+        ctx.client_auth_certificates.get_or_insert(certs);
+    }
+
+    count
+}
+
+#[no_mangle]
+pub extern "C" fn yaha_client_config_add_client_auth_key(ctx: *mut YahaNativeContext, auth_key: *const StringBuffer) -> usize {
+    let ctx = YahaNativeContextInternal::from_raw_context(ctx);
+    let keys: Vec<rustls::PrivateKey> = unsafe { rustls_pemfile::pkcs8_private_keys(&mut (*auth_key).to_bytes()).unwrap().into_iter().map(rustls::PrivateKey).collect() };
+
+    let count = keys.len();
+
+    if count > 0 {
+        ctx.client_auth_key.get_or_insert(keys[0].clone());
+    }
+
+    count
+}
+
 #[no_mangle]
 pub extern "C" fn yaha_client_config_skip_certificate_verification(ctx: *mut YahaNativeContext, val: bool) {
     let ctx = YahaNativeContextInternal::from_raw_context(ctx);
diff --git a/native/yaha_native/src/context.rs b/native/yaha_native/src/context.rs
index f9bdd05..ad41b0a 100644
--- a/native/yaha_native/src/context.rs
+++ b/native/yaha_native/src/context.rs
@@ -20,6 +20,8 @@ pub struct YahaNativeContextInternal {
     pub client_builder: Option<client::Builder>,
     pub skip_certificate_verification: Option<bool>,
     pub root_certificates: Option<rustls::RootCertStore>,
+    pub client_auth_certificates: Option<Vec<rustls::Certificate>>,
+    pub client_auth_key: Option<rustls::PrivateKey>,
     pub client: Option<Client<HttpsConnector<HttpConnector>, hyper::Body>>,
     pub on_status_code_and_headers_receive: OnStatusCodeAndHeadersReceive,
     pub on_receive: OnReceive,
@@ -42,6 +44,8 @@ impl YahaNativeContextInternal {
             client_builder: Some(Client::builder()),
             skip_certificate_verification: None,
             root_certificates: None,
+            client_auth_certificates: None,
+            client_auth_key: None,
             on_status_code_and_headers_receive,
             on_receive,
             on_complete,
@@ -66,14 +70,23 @@ impl YahaNativeContextInternal {
                 .with_custom_certificate_verifier(Arc::new(danger::NoCertificateVerification {}))
                 .with_no_client_auth();
         } else {
+            let tls_config_builder_root: rustls::ConfigBuilder<rustls::ClientConfig, rustls::client::WantsTransparencyPolicyOrClientCert>;
             if let Some(root_certificates) = &self.root_certificates {
-                tls_config = tls_config_builder
-                    .with_root_certificates(root_certificates.to_owned())
-                    .with_no_client_auth();
+                tls_config_builder_root = tls_config_builder.with_root_certificates(root_certificates.to_owned());
             } else {
-                tls_config = tls_config_builder
-                    .with_webpki_roots()
-                    .with_no_client_auth();
+                tls_config_builder_root = tls_config_builder.with_webpki_roots();
+            }
+
+            tls_config = if let Some(client_auth_certificates) = &self.client_auth_certificates {
+                if let Some(client_auth_key) = &self.client_auth_key {
+                    tls_config_builder_root.clone()
+                        .with_client_auth_cert(client_auth_certificates.to_owned(), client_auth_key.to_owned())
+                        .unwrap_or(tls_config_builder_root.with_no_client_auth())
+                } else {
+                    tls_config_builder_root.with_no_client_auth()
+                }
+            } else {
+                tls_config_builder_root.with_no_client_auth()
             }
         }
 
diff --git a/src/YetAnotherHttpHandler/NativeMethods.g.cs b/src/YetAnotherHttpHandler/NativeMethods.g.cs
index d38b53f..2db6c3a 100644
--- a/src/YetAnotherHttpHandler/NativeMethods.g.cs
+++ b/src/YetAnotherHttpHandler/NativeMethods.g.cs
@@ -42,6 +42,12 @@ internal static unsafe partial class NativeMethods
         [DllImport(__DllName, EntryPoint = "yaha_client_config_add_root_certificates", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
         public static extern nuint yaha_client_config_add_root_certificates(YahaNativeContext* ctx, StringBuffer* root_certs);
 
+        [DllImport(__DllName, EntryPoint = "yaha_client_config_add_client_auth_certificates", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        public static extern nuint yaha_client_config_add_client_auth_certificates(YahaNativeContext* ctx, StringBuffer* auth_certs);
+
+        [DllImport(__DllName, EntryPoint = "yaha_client_config_add_client_auth_key", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        public static extern nuint yaha_client_config_add_client_auth_key(YahaNativeContext* ctx, StringBuffer* auth_key);
+
         [DllImport(__DllName, EntryPoint = "yaha_client_config_skip_certificate_verification", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
         public static extern void yaha_client_config_skip_certificate_verification(YahaNativeContext* ctx, [MarshalAs(UnmanagedType.U1)] bool val);
 
diff --git a/src/YetAnotherHttpHandler/NativeMethodsFuncPtr.g.cs b/src/YetAnotherHttpHandler/NativeMethodsFuncPtr.g.cs
index 8665a29..cc5a64e 100644
--- a/src/YetAnotherHttpHandler/NativeMethodsFuncPtr.g.cs
+++ b/src/YetAnotherHttpHandler/NativeMethodsFuncPtr.g.cs
@@ -28,6 +28,12 @@ internal static unsafe partial class NativeMethodsFuncPtr
         [DllImport(__DllName, EntryPoint = "yaha_client_config_add_root_certificates", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
         public static extern nuint yaha_client_config_add_root_certificates(YahaNativeContext* ctx, StringBuffer* root_certs);
 
+        [DllImport(__DllName, EntryPoint = "yaha_client_config_add_client_auth_certificates", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        public static extern nuint yaha_client_config_add_client_auth_certificates(YahaNativeContext* ctx, StringBuffer* auth_certs);
+
+        [DllImport(__DllName, EntryPoint = "yaha_client_config_add_client_auth_key", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        public static extern nuint yaha_client_config_add_client_auth_key(YahaNativeContext* ctx, StringBuffer* auth_key);
+
         [DllImport(__DllName, EntryPoint = "yaha_client_config_skip_certificate_verification", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
         public static extern void yaha_client_config_skip_certificate_verification(YahaNativeContext* ctx, [MarshalAs(UnmanagedType.U1)] bool val);
 
diff --git a/src/YetAnotherHttpHandler/YetAnotherHttpHandler.cs b/src/YetAnotherHttpHandler/YetAnotherHttpHandler.cs
index c365f56..f0c2788 100644
--- a/src/YetAnotherHttpHandler/YetAnotherHttpHandler.cs
+++ b/src/YetAnotherHttpHandler/YetAnotherHttpHandler.cs
@@ -50,6 +50,16 @@ public class YetAnotherHttpHandler : HttpMessageHandler
         /// </summary>
         public string? RootCertificates { get => _settings.RootCertificates; set => _settings.RootCertificates = value; }
 
+        /// <summary>
+        /// Gets or sets a custom client auth certificates.
+        /// </summary>
+        public string? ClientAuthCertificates { get => _settings.ClientAuthCertificates; set => _settings.ClientAuthCertificates = value; }
+
+        /// <summary>
+        /// Gets or sets a custom client auth key.
+        /// </summary>
+        public string? ClientAuthKey { get => _settings.ClientAuthKey; set => _settings.ClientAuthKey = value; }
+
         /// <summary>
         /// Gets or sets the SETTINGS_INITIAL_WINDOW_SIZE option for HTTP2 stream-level flow control.
         /// </summary>
@@ -174,6 +184,8 @@ internal class NativeClientSettings
         public bool? Http2Only { get; set; }
         public bool? SkipCertificateVerification { get; set; }
         public string? RootCertificates { get; set; }
+        public string? ClientAuthCertificates { get; set; }
+        public string? ClientAuthKey { get; set; }
         public uint? Http2InitialStreamWindowSize { get; set; }
         public uint? Http2InitialConnectionWindowSize { get; set; }
         public bool? Http2AdaptiveWindow { get; set; }
@@ -193,6 +205,8 @@ public NativeClientSettings Clone()
                 Http2Only = this.Http2Only,
                 SkipCertificateVerification = this.SkipCertificateVerification,
                 RootCertificates = this.RootCertificates,
+                ClientAuthCertificates = this.ClientAuthCertificates,
+                ClientAuthKey = this.ClientAuthKey,
                 Http2InitialStreamWindowSize = this.Http2InitialStreamWindowSize,
                 Http2InitialConnectionWindowSize = this.Http2InitialConnectionWindowSize,
                 Http2AdaptiveWindow = this.Http2AdaptiveWindow,