diff --git a/src/tags_handlers/insertion_tags_handler.cc b/src/tags_handlers/insertion_tags_handler.cc
new file mode 100644
index 0000000..81c9f5e
--- /dev/null
+++ b/src/tags_handlers/insertion_tags_handler.cc
@@ -0,0 +1,21 @@
+#include "tags_handlers/insertion_tags_handler.h"
+#include "tags_handlers_errors.h"
+
+using namespace opustags;
+
+InsertionTagsHandler::InsertionTagsHandler(
+    const int streamno,
+    const std::string &tag_key,
+    const std::string &tag_value)
+    : StreamTagsHandler(streamno), tag_key(tag_key), tag_value(tag_value)
+{
+}
+
+bool InsertionTagsHandler::edit_impl(Tags &tags)
+{
+    if (tags.find(tag_key) != tags.end())
+        throw TagAlreadyExistsError(tag_key);
+
+    tags[tag_key] = tag_value;
+    return true;
+}
diff --git a/src/tags_handlers/insertion_tags_handler.h b/src/tags_handlers/insertion_tags_handler.h
new file mode 100644
index 0000000..889cc9d
--- /dev/null
+++ b/src/tags_handlers/insertion_tags_handler.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include "tags_handlers/stream_tags_handler.h"
+
+namespace opustags {
+
+    class InsertionTagsHandler : public StreamTagsHandler
+    {
+    public:
+        InsertionTagsHandler(
+            const int streamno,
+            const std::string &tag_key,
+            const std::string &tag_value);
+
+    protected:
+        bool edit_impl(Tags &) override;
+
+    private:
+        const std::string tag_key;
+        const std::string tag_value;
+    };
+
+}
diff --git a/src/tags_handlers_errors.cc b/src/tags_handlers_errors.cc
new file mode 100644
index 0000000..1f33c6d
--- /dev/null
+++ b/src/tags_handlers_errors.cc
@@ -0,0 +1,8 @@
+#include "tags_handlers_errors.h"
+
+using namespace opustags;
+
+TagAlreadyExistsError::TagAlreadyExistsError(const std::string &tag_key)
+    : std::runtime_error("Tag already exists: " + tag_key)
+{
+}
diff --git a/src/tags_handlers_errors.h b/src/tags_handlers_errors.h
new file mode 100644
index 0000000..99e5d56
--- /dev/null
+++ b/src/tags_handlers_errors.h
@@ -0,0 +1,12 @@
+#pragma once
+
+#include <stdexcept>
+
+namespace opustags {
+
+    struct TagAlreadyExistsError : std::runtime_error
+    {
+        TagAlreadyExistsError(const std::string &tag_key);
+    };
+
+}
diff --git a/tests/tags_handlers/insertion_tags_handler_test.cc b/tests/tags_handlers/insertion_tags_handler_test.cc
new file mode 100644
index 0000000..9167932
--- /dev/null
+++ b/tests/tags_handlers/insertion_tags_handler_test.cc
@@ -0,0 +1,19 @@
+#include "tags_handlers/insertion_tags_handler.h"
+#include "catch.h"
+
+using namespace opustags;
+
+TEST_CASE("Insertion tags handler test")
+{
+    Tags tags;
+    const auto streamno = 1;
+    const auto expected_tag_key = "tag_key";
+    const auto expected_tag_value = "tag_value";
+    InsertionTagsHandler handler(
+        streamno, expected_tag_key, expected_tag_value);
+
+    REQUIRE(handler.edit(streamno, tags));
+    REQUIRE(tags.size() == 1);
+    REQUIRE(tags[expected_tag_key] == expected_tag_value);
+    REQUIRE_THROWS(handler.edit(streamno, tags));
+}