diff --git a/c_src/ex_dtls/native.c b/c_src/ex_dtls/native.c
index 964e50f..93c38bb 100644
--- a/c_src/ex_dtls/native.c
+++ b/c_src/ex_dtls/native.c
@@ -108,6 +108,7 @@ UNIFEX_TERM do_init(UnifexEnv *env, char *mode_str, int dtls_srtp,
   state->x509 = NULL;
   state->mode = 0;
   state->hsk_finished = 0;
+  state->closed = 0;
   state->env = unifex_alloc_env(env);
 
   int mode;
@@ -244,6 +245,10 @@ UNIFEX_TERM get_cert_fingerprint(UnifexEnv *env, UnifexPayload *cert) {
 }
 
 UNIFEX_TERM do_handshake(UnifexEnv *env, State *state) {
+  if (state->closed == 1) {
+    return do_handshake_result_error_closed(env);
+  }
+
   SSL_do_handshake(state->ssl);
 
   UnifexPayload **gen_packets = NULL;
@@ -258,7 +263,7 @@ UNIFEX_TERM do_handshake(UnifexEnv *env, State *state) {
   } else {
     int timeout = get_timeout(state->ssl);
     UNIFEX_TERM res_term =
-        do_handshake_result(env, gen_packets, gen_packets_size, timeout);
+        do_handshake_result_ok(env, gen_packets, gen_packets_size, timeout);
     free_payload_array(gen_packets, gen_packets_size);
 
     return res_term;
@@ -266,6 +271,11 @@ UNIFEX_TERM do_handshake(UnifexEnv *env, State *state) {
 }
 
 UNIFEX_TERM write_data(UnifexEnv *env, State *state, UnifexPayload *payload) {
+  if (state->closed == 1) {
+    DEBUG("Cannot write, connection closed");
+    return write_data_result_error_closed(env);
+  }
+
   if (state->hsk_finished != 1) {
     DEBUG("Cannot write, handshake not finished");
     return write_data_result_error_handshake_not_finished(env);
@@ -303,6 +313,10 @@ UNIFEX_TERM write_data(UnifexEnv *env, State *state, UnifexPayload *payload) {
 }
 
 UNIFEX_TERM handle_data(UnifexEnv *env, State *state, UnifexPayload *payload) {
+  if (state->closed == 1) {
+    return handle_data_result_error_closed(env);
+  }
+
   (void)env;
 
   if (payload->size != 0) {
@@ -332,6 +346,32 @@ UNIFEX_TERM handle_data(UnifexEnv *env, State *state, UnifexPayload *payload) {
   }
 }
 
+// prefix close with exd (ex_dtls) as close is defined in unistd.h
+UNIFEX_TERM exd_close(UnifexEnv *env, State *state) {
+  if (state->closed == 1) {
+    return exd_close_result_ok(env, NULL, 0);
+  }
+
+  state->closed = 1;
+  if (SSL_shutdown(state->ssl) < 0) {
+    return exd_close_result_ok(env, NULL, 0);
+  } else {
+    UnifexPayload **gen_packets = NULL;
+    int gen_packets_size = 0;
+    read_pending_data(&gen_packets, &gen_packets_size, state);
+
+    if (gen_packets == NULL) {
+      return unifex_raise(state->env,
+                          "Close failed: couldn't read pending data");
+    } else {
+      UNIFEX_TERM res_term =
+          exd_close_result_ok(env, gen_packets, gen_packets_size);
+      free_payload_array(gen_packets, gen_packets_size);
+      return res_term;
+    }
+  }
+}
+
 UNIFEX_TERM handle_regular_read(State *state, char data[], int ret) {
   if (ret > 0) {
     UnifexPayload packets;
@@ -351,6 +391,7 @@ UNIFEX_TERM handle_read_error(State *state, int ret) {
   int error = SSL_get_error(state->ssl, ret);
   switch (error) {
   case SSL_ERROR_ZERO_RETURN:
+    state->closed = 1;
     return handle_data_result_error_peer_closed_for_writing(state->env);
   case SSL_ERROR_WANT_READ:
     DEBUG("SSL WANT READ. This is workaround. Did we get retransmission?");
@@ -452,6 +493,10 @@ UNIFEX_TERM handle_handshake_in_progress(State *state, int ret) {
 }
 
 UNIFEX_TERM handle_timeout(UnifexEnv *env, State *state) {
+  if (state->closed == 1) {
+    return handle_timeout_result_error_closed(env);
+  }
+
   long result = DTLSv1_handle_timeout(state->ssl);
   if (result != 1)
     return handle_timeout_result_ok(env);
diff --git a/c_src/ex_dtls/native.h b/c_src/ex_dtls/native.h
index 1c5365b..bcaf461 100644
--- a/c_src/ex_dtls/native.h
+++ b/c_src/ex_dtls/native.h
@@ -13,6 +13,7 @@ struct State {
   X509 *x509;
   int mode;
   int hsk_finished;
+  int closed;
 };
 
 #include "_generated/native.h"
diff --git a/c_src/ex_dtls/native.spec.exs b/c_src/ex_dtls/native.spec.exs
index 5d9cde5..8b5c2f7 100644
--- a/c_src/ex_dtls/native.spec.exs
+++ b/c_src/ex_dtls/native.spec.exs
@@ -21,11 +21,17 @@ spec get_peer_cert(state) :: payload | (nil :: label)
 
 spec get_cert_fingerprint(payload) :: payload
 
-spec do_handshake(state) :: {packets :: [payload], timeout :: int}
+spec do_handshake(state) :: {:ok :: label, packets :: [payload], timeout :: int} | {:error :: label, :closed :: label}
 
-spec handle_timeout(state) :: (:ok :: label) | {:retransmit :: label, packets :: [payload], timeout :: int}
+spec handle_timeout(state) ::
+       (:ok :: label)
+       | {:retransmit :: label, packets :: [payload], timeout :: int}
+       | {:error :: label, :closed :: label}
 
-spec write_data(state, packets :: payload) :: {:ok :: label, packets :: [payload]} | {:error :: label, :handshake_not_finished :: label}
+spec write_data(state, packets :: payload) ::
+       {:ok :: label, packets :: [payload]}
+       | {:error :: label, :handshake_not_finished :: label}
+       | {:error :: label, :closed :: label}
 
 spec handle_data(state, packets :: payload) ::
        {:ok :: label, packets :: payload}
@@ -34,5 +40,7 @@ spec handle_data(state, packets :: payload) ::
        | {:handshake_finished :: label, client_keying_material :: payload,
           server_keying_material :: payload, protection_profile :: int, packets :: [payload]}
        | {:error :: label, :peer_closed_for_writing :: label}
-       | {:error :: label, :handshake_error :: label
-}
+       | {:error :: label, :handshake_error :: label}
+       | {:error :: label, :closed :: label}
+
+spec exd_close(state) :: {:ok :: label, packets :: [payload]}
diff --git a/lib/ex_dtls.ex b/lib/ex_dtls.ex
index 9def56d..143ed69 100644
--- a/lib/ex_dtls.ex
+++ b/lib/ex_dtls.ex
@@ -139,7 +139,8 @@ defmodule ExDTLS do
 
   `timeout` is a time in ms after which `handle_timeout/1` should be called.
   """
-  @spec do_handshake(dtls()) :: {packets :: [binary()], timeout :: integer()}
+  @spec do_handshake(dtls()) ::
+          {:ok, packets :: [binary()], timeout :: integer()} | {:error, :closed}
   defdelegate do_handshake(dtls), to: Native
 
   @doc """
@@ -148,7 +149,7 @@ defmodule ExDTLS do
   Generates encrypted packets that need to be passed to the second host.
   """
   @spec write_data(dtls(), data :: binary()) ::
-          {:ok, packets :: [binary()]} | {:error, :handshake_not_finished}
+          {:ok, packets :: [binary()]} | {:error, :handshake_not_finished | :closed}
   defdelegate write_data(dtls, data), to: Native
 
   @doc """
@@ -172,7 +173,7 @@ defmodule ExDTLS do
              remote_keying_material :: binary(), protection_profile_t(), packets :: [binary()]}
           | {:handshake_finished, local_keying_material :: binary(),
              remote_keying_material :: binary(), protection_profile_t()}
-          | {:error, :handshake_error | :peer_closed_for_writing}
+          | {:error, :handshake_error | :peer_closed_for_writing | :closed}
   def handle_data(dtls, packets) do
     case Native.handle_data(dtls, packets) do
       {:handshake_finished, lkm, rkm, protection_profile, []} ->
@@ -192,6 +193,16 @@ defmodule ExDTLS do
 
   If there is no timeout to handle, simple `{:ok, dtls()}` tuple is returned.
   """
-  @spec handle_timeout(dtls()) :: :ok | {:retransmit, packets :: [binary()], timeout :: integer()}
+  @spec handle_timeout(dtls()) ::
+          :ok | {:retransmit, packets :: [binary()], timeout :: integer()} | {:error, :closed}
   defdelegate handle_timeout(dtls), to: Native
+
+  @doc """
+  Irreversibly closes DTLS session.
+
+  If a handshake has been finished, this function will generate `close_notify` DTLS alert
+  that should be sent to the other side.
+  """
+  @spec close(dtls()) :: {:ok, packets :: [binary()]}
+  defdelegate close(dtls), to: Native, as: :exd_close
 end
diff --git a/test/integration_test.exs b/test/integration_test.exs
index 9336d14..4c65dac 100644
--- a/test/integration_test.exs
+++ b/test/integration_test.exs
@@ -5,7 +5,7 @@ defmodule ExDTLS.IntegrationTest do
     rx_dtls = ExDTLS.init(mode: :server, dtls_srtp: true, verify_peer: true)
     tx_dtls = ExDTLS.init(mode: :client, dtls_srtp: true, verify_peer: true)
 
-    {packets, _timeout} = ExDTLS.do_handshake(tx_dtls)
+    {:ok, packets, _timeout} = ExDTLS.do_handshake(tx_dtls)
 
     assert :ok == loop({rx_dtls, false}, {tx_dtls, false}, packets)
 
@@ -17,7 +17,7 @@ defmodule ExDTLS.IntegrationTest do
     rx_dtls = ExDTLS.init(mode: :server, dtls_srtp: true)
     tx_dtls = ExDTLS.init(mode: :client, dtls_srtp: true)
 
-    {packets, _timeout} = ExDTLS.do_handshake(tx_dtls)
+    {:ok, packets, _timeout} = ExDTLS.do_handshake(tx_dtls)
 
     assert :ok == loop({rx_dtls, false}, {tx_dtls, false}, packets)
 
@@ -34,7 +34,7 @@ defmodule ExDTLS.IntegrationTest do
     assert {:error, :handshake_not_finished} = ExDTLS.write_data(sr_dtls, <<1, 2, 3>>)
     assert {:error, :handshake_not_finished} = ExDTLS.write_data(cl_dtls, <<1, 2, 3>>)
 
-    {packets, _timeout} = ExDTLS.do_handshake(cl_dtls)
+    {:ok, packets, _timeout} = ExDTLS.do_handshake(cl_dtls)
     assert :ok == loop({sr_dtls, false}, {cl_dtls, false}, packets)
 
     msg = <<1, 3, 2, 5>>
@@ -55,11 +55,53 @@ defmodule ExDTLS.IntegrationTest do
 
     tx_dtls = ExDTLS.init(mode: :client, dtls_srtp: true, verify_peer: true)
 
-    {packets, _timeout} = ExDTLS.do_handshake(tx_dtls)
+    {:ok, packets, _timeout} = ExDTLS.do_handshake(tx_dtls)
     {:handshake_packets, packets, _timeout} = feed_packets(rx_dtls, packets)
     assert {:error, :handshake_error} = feed_packets(tx_dtls, packets)
   end
 
+  describe "close/1" do
+    test "before handshake has finished (client mode)" do
+      dtls = ExDTLS.init(mode: :client, dtls_srtp: true, verify_peer: true)
+      assert {:ok, []} = ExDTLS.close(dtls)
+      # assert that handshake can't be started
+      assert {:error, :closed} = ExDTLS.do_handshake(dtls)
+    end
+
+    test "before handshake has finished (server mode)" do
+      dtls = ExDTLS.init(mode: :server, dtls_srtp: true, verify_peer: true)
+      assert {:ok, []} = ExDTLS.close(dtls)
+      # assert that handshake can't be started
+      assert {:error, :closed} = ExDTLS.do_handshake(dtls)
+    end
+
+    test "after handshake has finished (client mode)" do
+      rx_dtls = ExDTLS.init(mode: :server, dtls_srtp: true, verify_peer: true)
+      tx_dtls = ExDTLS.init(mode: :client, dtls_srtp: true, verify_peer: true)
+
+      {:ok, packets, _timeout} = ExDTLS.do_handshake(tx_dtls)
+
+      assert :ok == loop({rx_dtls, false}, {tx_dtls, false}, packets)
+      assert {:ok, [packet]} = ExDTLS.close(tx_dtls)
+      assert {:error, :peer_closed_for_writing} = ExDTLS.handle_data(rx_dtls, packet)
+      assert {:error, :closed} = ExDTLS.handle_timeout(tx_dtls)
+      assert {:error, :closed} = ExDTLS.handle_timeout(rx_dtls)
+    end
+
+    test "after handshake has finished (server mode)" do
+      rx_dtls = ExDTLS.init(mode: :server, dtls_srtp: true, verify_peer: true)
+      tx_dtls = ExDTLS.init(mode: :client, dtls_srtp: true, verify_peer: true)
+
+      {:ok, packets, _timeout} = ExDTLS.do_handshake(tx_dtls)
+
+      assert :ok == loop({rx_dtls, false}, {tx_dtls, false}, packets)
+      assert {:ok, [packet]} = ExDTLS.close(rx_dtls)
+      assert {:error, :peer_closed_for_writing} = ExDTLS.handle_data(tx_dtls, packet)
+      assert {:error, :closed} = ExDTLS.handle_timeout(tx_dtls)
+      assert {:error, :closed} = ExDTLS.handle_timeout(rx_dtls)
+    end
+  end
+
   defp loop({_dtls1, true}, {_dtls2, true}, _packets) do
     :ok
   end
diff --git a/test/retransmission_test.exs b/test/retransmission_test.exs
index ffbb88d..f7ec391 100644
--- a/test/retransmission_test.exs
+++ b/test/retransmission_test.exs
@@ -5,7 +5,7 @@ defmodule ExDTLS.RetransmissionTest do
     rx_dtls = ExDTLS.init(mode: :server, dtls_srtp: true)
     tx_dtls = ExDTLS.init(mode: :client, dtls_srtp: true)
 
-    {_packets, timeout} = ExDTLS.do_handshake(tx_dtls)
+    {:ok, _packets, timeout} = ExDTLS.do_handshake(tx_dtls)
     Process.send_after(self(), {:handle_timeout, :tx}, timeout)
     {:retransmit, packets, timeout} = wait_for_timeout(tx_dtls, :tx)
     Process.send_after(self(), {:handle_timeout, :tx}, timeout)