diff --git a/src/RequestHeaders.php b/src/RequestHeaders.php
index 64bae33..52105f3 100644
--- a/src/RequestHeaders.php
+++ b/src/RequestHeaders.php
@@ -47,6 +47,23 @@ public function add(string $key, string $value): void
         }
     }
 
+    /**
+     * Try to add a value to the existing values for that specific header if it's not already set.
+     * @param string $key
+     * @param string $value
+     * @return boolean if the value have been added
+     */
+    public function tryAdd(string $key, string $value): bool
+    {
+        $lowercaseKey = strtolower($key);
+        if (array_key_exists($lowercaseKey, $this->headers)) {
+            return false;
+        } else {
+            $this->headers[$lowercaseKey] = [$value => true];
+            return true;
+        }
+    }
+
     /**
      * Returns the lowercase version of a string.
      * @param string $key
diff --git a/src/RequestInformation.php b/src/RequestInformation.php
index bab234d..baae631 100644
--- a/src/RequestInformation.php
+++ b/src/RequestInformation.php
@@ -153,7 +153,7 @@ public function removeRequestOptions(RequestOption ...$options): void {
      */
     public function setStreamContent(StreamInterface $value): void {
         $this->content = $value;
-        $this->headers->add(self::$contentTypeHeader, self::$binaryContentType);
+        $this->headers->tryAdd(self::$contentTypeHeader, self::$binaryContentType);
     }
 
     /**
@@ -171,7 +171,7 @@ public function setContentFromParsable(RequestAdapter $requestAdapter, string $c
             $writer = $requestAdapter->getSerializationWriterFactory()->getSerializationWriter($contentType);
             $writer->writeObjectValue(null, $value);
             $span->setAttribute(ObservabilityOptions::REQUEST_TYPE_KEY, get_class($value));
-            $this->headers->add(self::$contentTypeHeader, $contentType);
+            $this->headers->tryAdd(self::$contentTypeHeader, $contentType);
             $this->content = $writer->getSerializedContent();
             $span->setStatus(StatusCode::STATUS_OK);
         } catch (Exception $exception) {
@@ -205,7 +205,7 @@ public function setContentFromParsableCollection(RequestAdapter $requestAdapter,
             if (!empty($values)) {
                 $span->setAttribute(ObservabilityOptions::REQUEST_TYPE_KEY, get_class($values[0]));
             }
-            $this->headers->add(self::$contentTypeHeader, $contentType);
+            $this->headers->tryAdd(self::$contentTypeHeader, $contentType);
             $this->content = $writer->getSerializedContent();
         } catch (Exception $exception) {
             throw new RuntimeException('could not serialize payload.', 1, $exception);
@@ -232,7 +232,7 @@ public function setContentFromScalar(RequestAdapter $requestAdapter, string $con
             $writer->writeAnyValue(null, $value);
             $span->setAttribute(self::$contentTypeHeader, $contentType);
             $span->setAttribute(ObservabilityOptions::REQUEST_TYPE_KEY, gettype($value));
-            $this->headers->add(self::$contentTypeHeader, $contentType);
+            $this->headers->tryAdd(self::$contentTypeHeader, $contentType);
             $this->content = $writer->getSerializedContent();
             $span->setStatus(StatusCode::STATUS_OK);
         } catch (Exception $exception) {
@@ -265,7 +265,7 @@ public function setContentFromScalarCollection(RequestAdapter $requestAdapter, s
             if (!empty($values)) {
                 $span->setAttribute(ObservabilityOptions::REQUEST_TYPE_KEY, gettype($values[0]));
             }
-            $this->headers->add(self::$contentTypeHeader, $contentType);
+            $this->headers->tryAdd(self::$contentTypeHeader, $contentType);
             $this->content = $writer->getSerializedContent();
             $span->setStatus(StatusCode::STATUS_OK);
         } catch (Exception $exception) {
diff --git a/tests/RequestHeadersTest.php b/tests/RequestHeadersTest.php
index b60c9a1..9d2c86b 100644
--- a/tests/RequestHeadersTest.php
+++ b/tests/RequestHeadersTest.php
@@ -89,6 +89,17 @@ public function testCanAdd(): void
         $this->assertEquals(["value", "value2", "VALUE2"], $headers->get($key));
     }
 
+    public function testCanTryAdd(): void
+    {
+        $headers = new RequestHeaders();
+        $key = "key";
+        $this->assertTrue($headers->tryAdd($key, "value"));
+        $this->assertEquals(["value"], $headers->get($key));
+
+        $this->assertFalse($headers->tryAdd($key, "value2"));
+        $this->assertEquals(["value"], $headers->get($key));
+    }
+
     public function testCanPutAll(): void
     {
         $headers = new RequestHeaders();