diff --git a/packages/interactive_media_ads/CHANGELOG.md b/packages/interactive_media_ads/CHANGELOG.md
index 20b13ddb8282..347340ae32bc 100644
--- a/packages/interactive_media_ads/CHANGELOG.md
+++ b/packages/interactive_media_ads/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.2.3+12
+
+* Fixes appending request agent to ad tags that contain a query.
+
 ## 0.2.3+11
 
 * Updates pigeon generated code to fix `ImplicitSamInstance` and `SyntheticAccessor` Kotlin lint
diff --git a/packages/interactive_media_ads/android/src/main/kotlin/dev/flutter/packages/interactive_media_ads/AdsRequestProxyApi.kt b/packages/interactive_media_ads/android/src/main/kotlin/dev/flutter/packages/interactive_media_ads/AdsRequestProxyApi.kt
index d5229e4aa476..2e46d3435d50 100644
--- a/packages/interactive_media_ads/android/src/main/kotlin/dev/flutter/packages/interactive_media_ads/AdsRequestProxyApi.kt
+++ b/packages/interactive_media_ads/android/src/main/kotlin/dev/flutter/packages/interactive_media_ads/AdsRequestProxyApi.kt
@@ -21,15 +21,16 @@ class AdsRequestProxyApi(override val pigeonRegistrar: ProxyApiRegistrar) :
      *
      * This must match the version in pubspec.yaml.
      */
-    const val pluginVersion = "0.2.3+11"
+    const val pluginVersion = "0.2.3+12"
   }
 
   override fun setAdTagUrl(pigeon_instance: AdsRequest, adTagUrl: String) {
-    // Ensure adTag can append a custom parameter.
-    require(adTagUrl.contains("?"))
-    require(!adTagUrl.contains("#"))
-
-    pigeon_instance.adTagUrl = "$adTagUrl&request_agent=Flutter-IMA-$pluginVersion"
+    // Add a request agent only if the adTagUrl can append a custom parameter.
+    if (!adTagUrl.contains("#") && adTagUrl.contains("?")) {
+      pigeon_instance.adTagUrl = "$adTagUrl&request_agent=Flutter-IMA-$pluginVersion"
+    } else {
+      pigeon_instance.adTagUrl = adTagUrl
+    }
   }
 
   override fun setContentProgressProvider(
diff --git a/packages/interactive_media_ads/android/src/test/kotlin/dev/flutter/packages/interactive_media_ads/AdsRequestProxyApiTest.kt b/packages/interactive_media_ads/android/src/test/kotlin/dev/flutter/packages/interactive_media_ads/AdsRequestProxyApiTest.kt
index 42f0cc88b84e..e3e9e2baf557 100644
--- a/packages/interactive_media_ads/android/src/test/kotlin/dev/flutter/packages/interactive_media_ads/AdsRequestProxyApiTest.kt
+++ b/packages/interactive_media_ads/android/src/test/kotlin/dev/flutter/packages/interactive_media_ads/AdsRequestProxyApiTest.kt
@@ -22,6 +22,19 @@ class AdsRequestProxyApiTest {
         "adTag?&request_agent=Flutter-IMA-${AdsRequestProxyApi.pluginVersion}"
   }
 
+  @Test
+  fun setAdTagUrlDoesNotAddRequestAgentToIncompatibleUrls() {
+    val api = TestProxyApiRegistrar().getPigeonApiAdsRequest()
+
+    val instance = mock<AdsRequest>()
+
+    api.setAdTagUrl(instance, "adTag#")
+    verify(instance).adTagUrl = "adTag#"
+
+    api.setAdTagUrl(instance, "adTag?#")
+    verify(instance).adTagUrl = "adTag?#"
+  }
+
   @Test
   fun setContentProgressProvider() {
     val api = TestProxyApiRegistrar().getPigeonApiAdsRequest()
diff --git a/packages/interactive_media_ads/example/ios/RunnerTests/AdsRequestTests.swift b/packages/interactive_media_ads/example/ios/RunnerTests/AdsRequestTests.swift
index 21b52654ad9d..c7b6c0b4ed63 100644
--- a/packages/interactive_media_ads/example/ios/RunnerTests/AdsRequestTests.swift
+++ b/packages/interactive_media_ads/example/ios/RunnerTests/AdsRequestTests.swift
@@ -25,4 +25,28 @@ final class AdsRequestTests: XCTestCase {
       "adTag?&request_agent=Flutter-IMA-\(AdsRequestProxyAPIDelegate.pluginVersion)")
     XCTAssertIdentical(instance?.adDisplayContainer, container)
   }
+
+  func testPigeonDefaultConstructorDoesNotAddRequestAgentToIncompatibleURLs() {
+    let registrar = TestProxyApiRegistrar()
+    let api = registrar.apiDelegate.pigeonApiIMAAdsRequest(registrar)
+
+    let container = IMAAdDisplayContainer(adContainer: UIView(), viewController: nil)
+    let contentPlayhead = ContentPlayheadImpl()
+
+    var instance = try? api.pigeonDelegate.pigeonDefaultConstructor(
+      pigeonApi: api, adTagUrl: "adTag#", adDisplayContainer: container,
+      contentPlayhead: contentPlayhead)
+    XCTAssertNotNil(instance)
+    XCTAssertEqual(
+      instance?.adTagUrl,
+      "adTag#")
+
+    instance = try? api.pigeonDelegate.pigeonDefaultConstructor(
+      pigeonApi: api, adTagUrl: "adTag#?", adDisplayContainer: container,
+      contentPlayhead: contentPlayhead)
+    XCTAssertNotNil(instance)
+    XCTAssertEqual(
+      instance?.adTagUrl,
+      "adTag#?")
+  }
 }
diff --git a/packages/interactive_media_ads/ios/interactive_media_ads/Sources/interactive_media_ads/AdsRequestProxyAPIDelegate.swift b/packages/interactive_media_ads/ios/interactive_media_ads/Sources/interactive_media_ads/AdsRequestProxyAPIDelegate.swift
index 8f926613c6ea..c6ce12f4793e 100644
--- a/packages/interactive_media_ads/ios/interactive_media_ads/Sources/interactive_media_ads/AdsRequestProxyAPIDelegate.swift
+++ b/packages/interactive_media_ads/ios/interactive_media_ads/Sources/interactive_media_ads/AdsRequestProxyAPIDelegate.swift
@@ -13,20 +13,20 @@ class AdsRequestProxyAPIDelegate: PigeonApiDelegateIMAAdsRequest {
   /// The current version of the `interactive_media_ads` plugin.
   ///
   /// This must match the version in pubspec.yaml.
-  static let pluginVersion = "0.2.3+11"
+  static let pluginVersion = "0.2.3+12"
 
   func pigeonDefaultConstructor(
     pigeonApi: PigeonApiIMAAdsRequest, adTagUrl: String, adDisplayContainer: IMAAdDisplayContainer,
     contentPlayhead: IMAContentPlayhead?
   ) throws -> IMAAdsRequest {
-    // Ensure adTag can append a custom parameter.
-    assert(adTagUrl.contains("?"))
-    assert(!adTagUrl.contains("#"))
+    // Add a request agent only if the adTagUrl can append a custom parameter.
+    let modifiedURL =
+      !adTagUrl.contains("#") && adTagUrl.contains("?")
+      ? "\(adTagUrl)&request_agent=Flutter-IMA-\(AdsRequestProxyAPIDelegate.pluginVersion)"
+      : adTagUrl
 
-    let adTagWithRequestAgent =
-      "\(adTagUrl)&request_agent=Flutter-IMA-\(AdsRequestProxyAPIDelegate.pluginVersion)"
     return IMAAdsRequest(
-      adTagUrl: adTagWithRequestAgent, adDisplayContainer: adDisplayContainer,
+      adTagUrl: modifiedURL, adDisplayContainer: adDisplayContainer,
       contentPlayhead: contentPlayhead as? ContentPlayheadImpl, userContext: nil)
   }
 }
diff --git a/packages/interactive_media_ads/pubspec.yaml b/packages/interactive_media_ads/pubspec.yaml
index 2c4a1d24cd45..69a19874a871 100644
--- a/packages/interactive_media_ads/pubspec.yaml
+++ b/packages/interactive_media_ads/pubspec.yaml
@@ -2,7 +2,7 @@ name: interactive_media_ads
 description: A Flutter plugin for using the Interactive Media Ads SDKs on Android and iOS.
 repository: https://github.com/flutter/packages/tree/main/packages/interactive_media_ads
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+interactive_media_ads%22
-version: 0.2.3+11 # This must match the version in
+version: 0.2.3+12 # This must match the version in
   # `android/src/main/kotlin/dev/flutter/packages/interactive_media_ads/AdsRequestProxyApi.kt` and
   # `ios/interactive_media_ads/Sources/interactive_media_ads/AdsRequestProxyAPIDelegate.swift`