diff --git a/Scripts/BuildPhases/LintNestedFrameworks.sh b/Scripts/BuildPhases/LintNestedFrameworks.sh
new file mode 100755
index 000000000000..e7a42541664b
--- /dev/null
+++ b/Scripts/BuildPhases/LintNestedFrameworks.sh
@@ -0,0 +1,27 @@
+#!/bin/sh -eu
+
+set pipefail
+
+# Nested frameworks (i.e. having a Frameworks/ folder inside *.app/Frameworks/.framework) is invalid and will make the build be rejected during TestFlight validation.
+#
+# See also https://github.com/woocommerce/woocommerce-ios/pull/4226
+
+# This script is intended to be used as a Build Phase on the main app target, as the very last build phase (and especially after the "Embed Frameworks" phase)
+
+NESTED_FMKS_DIRS=$(find "${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}" -name Frameworks -depth 2)
+if [ -z "$NESTED_FMKS_DIRS" ]; then
+    echo "✅ No nested framework found, you're good to go!"
+else
+    echo "❌ Found nested \`Frameworks\` folder inside frameworks of final bundle."
+    for fmk_dir in $NESTED_FMKS_DIRS; do
+        # Extract the name of the parent framework containing the nested ones
+        parent_fmk=$(basename $(dirname $fmk_dir) .framework)
+        # Extract the list of frameworks nested inside that parent framework. In the next command:
+        #  * `-depth 1` is to avoid logging cases of "C nested in B itself nested in A" (2+ levels of nesting), since C nested in B will already be logged when looping on fmk_dir=B, so no need to log it during fmk_dir=A too.
+        #  * The `sed` command removes the leading `./` in the paths returned by `find`, then quote the results in backticks for nicer formatting in final message.
+        #  * The `tr` command joins all the lines (= found frameworks) with a `,`. Note that this will result in an extra comma at the end of the list too, but we'll get rid of that in the final message using ${nested_fmks%,} bash substitution.
+        nested_fmks=$(cd "${fmk_dir}" && find . -name '*.framework' -depth 1 | sed "s:^./\(.*\)$:\`\1\`:" | tr '\n' ',')
+        echo "error: Found nested frameworks in ${fmk_dir} -- Such a configuration is invalid and will be rejected by TestFlight. Please fix by choosing 'Do Not Embed' for the nested framework(s) ${nested_fmks%,} within the \`${parent_fmk}\` Xcode project which links to them. See paNNhX-ee-p2."
+    done
+    exit 1
+fi
diff --git a/WordPress/WordPress.xcodeproj/project.pbxproj b/WordPress/WordPress.xcodeproj/project.pbxproj
index 8e5c46a2ad67..255aab730ade 100644
--- a/WordPress/WordPress.xcodeproj/project.pbxproj
+++ b/WordPress/WordPress.xcodeproj/project.pbxproj
@@ -18419,6 +18419,7 @@
 				37399571B0D91BBEAE911024 /* [CP] Embed Pods Frameworks */,
 				920B9A6DAD47189622A86A9C /* [CP] Copy Pods Resources */,
 				E1C5456F219F10E000896227 /* Copy Gutenberg JS */,
+				3FF795712A6671DB00F27B17 /* Lint against nested frameworks */,
 			);
 			buildRules = (
 			);
@@ -18715,6 +18716,7 @@
 				FABB264A2602FC2C00C8785C /* [CP] Embed Pods Frameworks */,
 				FABB264B2602FC2C00C8785C /* [CP] Copy Pods Resources */,
 				FABB264C2602FC2C00C8785C /* Copy Gutenberg JS */,
+				3FF795732A66730200F27B17 /* Lint against nested frameworks */,
 			);
 			buildRules = (
 			);
@@ -20230,6 +20232,43 @@
 			shellPath = /bin/sh;
 			shellScript = "$SRCROOT/../Scripts/BuildPhases/GenerateCredentials.sh\n";
 		};
+		3FF795712A6671DB00F27B17 /* Lint against nested frameworks */ = {
+			isa = PBXShellScriptBuildPhase;
+			alwaysOutOfDate = 1;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputFileListPaths = (
+			);
+			inputPaths = (
+			);
+			name = "Lint against nested frameworks";
+			outputFileListPaths = (
+			);
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "\"$SRCROOT/../Scripts/BuildPhases/LintNestedFrameworks.sh\"\n";
+		};
+		3FF795732A66730200F27B17 /* Lint against nested frameworks */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputFileListPaths = (
+			);
+			inputPaths = (
+			);
+			name = "Lint against nested frameworks";
+			outputFileListPaths = (
+			);
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "\"$SRCROOT/../Scripts/BuildPhases/LintNestedFrameworks.sh\"\n";
+		};
 		49AE9271B82C7D67430387FA /* [CP] Embed Pods Frameworks */ = {
 			isa = PBXShellScriptBuildPhase;
 			buildActionMask = 2147483647;