diff --git a/bson/build.gradle.kts b/bson/build.gradle.kts
index 810a16e2..1081a0df 100644
--- a/bson/build.gradle.kts
+++ b/bson/build.gradle.kts
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024-2025, OpenSavvy and contributors.
+ * Copyright (c) 2024-2026, OpenSavvy and contributors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -65,6 +65,10 @@ kotlin {
 		implementation(libsCommon.opensavvy.prepared.testBalloon)
 		implementation(libsCommon.kotlin.test)
 	}
+
+	sourceSets.jvmMain.dependencies {
+		compileOnly(libs.mongodb.kotlinx.serialization)
+	}
 }
 
 library {
diff --git a/bson/src/commonMain/kotlin/types/ObjectId.kt b/bson/src/commonMain/kotlin/types/ObjectId.kt
index 4e43de7d..cc107efc 100644
--- a/bson/src/commonMain/kotlin/types/ObjectId.kt
+++ b/bson/src/commonMain/kotlin/types/ObjectId.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2025, OpenSavvy and contributors.
+ * Copyright (c) 2025-2026, OpenSavvy and contributors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -285,14 +285,41 @@ class ObjectId : Comparable<ObjectId> {
 
 		@LowLevelApi
 		override fun serialize(encoder: Encoder, value: ObjectId) {
-			encoder.encodeString(value.hex)
+			serializeObjectIdPlatformSpecific(encoder, value)
 		}
 
 		override fun deserialize(decoder: Decoder): ObjectId =
-			decoder.decodeString().let(::ObjectId)
+			deserializeObjectIdPlatformSpecific(decoder)
 	}
 }
 
+@ExperimentalTime
+internal fun serializeObjectIdAsString(encoder: Encoder, value: ObjectId) {
+	encoder.encodeString(value.hex)
+}
+
+@ExperimentalTime
+internal fun deserializeObjectIdAsString(decoder: Decoder): ObjectId =
+	decoder.decodeString().let(::ObjectId)
+
+/**
+ * On the JVM, when using KotlinX.Serialization with the official driver, we must hard-code a different behavior.
+ *
+ * All non-JVM platforms implement this function by calling [serializeObjectIdAsString].
+ * This could be simplified with [KT-20427](https://youtrack.jetbrains.com/projects/KT/issues/KT-20427).
+ */
+@ExperimentalTime
+internal expect fun serializeObjectIdPlatformSpecific(encoder: Encoder, value: ObjectId)
+
+/**
+ * On the JVM, when using KotlinX.Serialization with the official driver, we must hard-code a different behavior.
+ *
+ * All non-JVM platforms implement this function by calling [deserializeObjectIdAsString].
+ * This could be simplified with [KT-20427](https://youtrack.jetbrains.com/projects/KT/issues/KT-20427).
+ */
+@ExperimentalTime
+internal expect fun deserializeObjectIdPlatformSpecific(decoder: Decoder): ObjectId
+
 @ExperimentalTime
 operator fun Instant.compareTo(objectId: ObjectId): Int =
 	-objectId.compareTo(this)
diff --git a/bson/src/jvmMain/kotlin/types/ObjectId.jvm.kt b/bson/src/jvmMain/kotlin/types/ObjectId.jvm.kt
new file mode 100644
index 00000000..dc3b7879
--- /dev/null
+++ b/bson/src/jvmMain/kotlin/types/ObjectId.jvm.kt
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2026, OpenSavvy and contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package opensavvy.ktmongo.bson.types
+
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+import org.bson.codecs.kotlinx.BsonDecoder
+import org.bson.codecs.kotlinx.BsonEncoder
+import kotlin.time.ExperimentalTime
+
+private val isOfficialKotlinSerializationEnabled =
+	ClassLoader.getSystemClassLoader().loadClass("org.bson.codecs.kotlinx.BsonEncoder") != null
+
+@OptIn(ExperimentalTime::class, ExperimentalSerializationApi::class)
+internal actual fun serializeObjectIdPlatformSpecific(encoder: Encoder, value: ObjectId) {
+	if (isOfficialKotlinSerializationEnabled && encoder is BsonEncoder) {
+		encoder.encodeObjectId(org.bson.types.ObjectId(value.bytes))
+	} else {
+		serializeObjectIdAsString(encoder, value)
+	}
+}
+
+@OptIn(ExperimentalSerializationApi::class)
+@ExperimentalTime
+internal actual fun deserializeObjectIdPlatformSpecific(decoder: Decoder): ObjectId =
+	if (isOfficialKotlinSerializationEnabled && decoder is BsonDecoder)
+		ObjectId(decoder.decodeObjectId().toByteArray())
+	else
+		deserializeObjectIdAsString(decoder)
diff --git a/bson/src/nativeMain/kotlin/types/ObjectId.native.kt b/bson/src/nativeMain/kotlin/types/ObjectId.native.kt
new file mode 100644
index 00000000..cdb32a8d
--- /dev/null
+++ b/bson/src/nativeMain/kotlin/types/ObjectId.native.kt
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2026, OpenSavvy and contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package opensavvy.ktmongo.bson.types
+
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+import kotlin.time.ExperimentalTime
+
+@ExperimentalTime
+internal actual fun serializeObjectIdPlatformSpecific(encoder: Encoder, value: ObjectId) {
+	serializeObjectIdAsString(encoder, value)
+}
+
+@ExperimentalTime
+internal actual fun deserializeObjectIdPlatformSpecific(decoder: Decoder): ObjectId =
+	deserializeObjectIdAsString(decoder)
diff --git a/bson/src/wasmWasiMain/kotlin/types/ObjectId.wasmWasi.kt b/bson/src/wasmWasiMain/kotlin/types/ObjectId.wasmWasi.kt
new file mode 100644
index 00000000..cdb32a8d
--- /dev/null
+++ b/bson/src/wasmWasiMain/kotlin/types/ObjectId.wasmWasi.kt
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2026, OpenSavvy and contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package opensavvy.ktmongo.bson.types
+
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+import kotlin.time.ExperimentalTime
+
+@ExperimentalTime
+internal actual fun serializeObjectIdPlatformSpecific(encoder: Encoder, value: ObjectId) {
+	serializeObjectIdAsString(encoder, value)
+}
+
+@ExperimentalTime
+internal actual fun deserializeObjectIdPlatformSpecific(decoder: Decoder): ObjectId =
+	deserializeObjectIdAsString(decoder)
diff --git a/bson/src/webMain/kotlin/types/ObjectId.web.kt b/bson/src/webMain/kotlin/types/ObjectId.web.kt
new file mode 100644
index 00000000..cdb32a8d
--- /dev/null
+++ b/bson/src/webMain/kotlin/types/ObjectId.web.kt
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2026, OpenSavvy and contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package opensavvy.ktmongo.bson.types
+
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+import kotlin.time.ExperimentalTime
+
+@ExperimentalTime
+internal actual fun serializeObjectIdPlatformSpecific(encoder: Encoder, value: ObjectId) {
+	serializeObjectIdAsString(encoder, value)
+}
+
+@ExperimentalTime
+internal actual fun deserializeObjectIdPlatformSpecific(decoder: Decoder): ObjectId =
+	deserializeObjectIdAsString(decoder)