diff --git a/src/tests/build.cmd b/src/tests/build.cmd
index b2d7e5d102a61c..1f90861cde5a17 100644
--- a/src/tests/build.cmd
+++ b/src/tests/build.cmd
@@ -355,9 +355,15 @@ echo All arguments are optional and case-insensitive, and the '-' prefix is opti
 echo.
 echo.-? -h --help: View this message.
 echo.
-echo Build architecture: one of "x64", "x86", "arm64" ^(default: x64^).
+echo Build architecture: one of "x64", "x86", "arm64", "wasm" ^(default: x64^).
 echo Build type: one of "Debug", "Checked", "Release" ^(default: Debug^).
 echo.
+echo Build target OS options:
+echo     os ^<value^>: Set the target OS. Common values: windows ^(default^), linux, osx, android,
+echo         ios, iossimulator, tvos, tvossimulator, maccatalyst, browser, wasi.
+echo     browser: Shorthand for "os browser" ^(typically combine with "wasm", for example "wasm browser"^).
+echo     wasi: Shorthand for "os wasi" ^(typically combine with "wasm", for example "wasm wasi"^).
+echo.
 echo -Rebuild: Clean up all test artifacts prior to building tests.
 echo -SkipRestorePackages: Skip package restore.
 echo -SkipManaged: Skip the managed tests build.
@@ -374,6 +380,7 @@ echo -NativeAOT: Builds the tests for Native AOT compilation.
 echo -Perfmap: Emit perfmap symbol files when compiling the framework assemblies using Crossgen2.
 echo -AllTargets: Build managed tests for all target platforms (including test projects in which CLRTestTargetUnsupported resolves to true).
 echo -ExcludeMonoFailures, Mono: Build the tests for the Mono runtime honoring mono-specific issues.
+echo -CoreCLR: Build tests targeting the CoreCLR runtime (default; opposite of -Mono/-ExcludeMonoFailures).
 echo.
 echo     Set to "" to disable default exclusion file.
 echo -Priority ^<N^> : specify a set of tests that will be built and run, with priority N.
diff --git a/src/tests/build.sh b/src/tests/build.sh
index a0709d7386517c..f18f28ee740369 100755
--- a/src/tests/build.sh
+++ b/src/tests/build.sh
@@ -136,6 +136,12 @@ build_Tests()
 usage_list=()
 usage_list+=("All arguments are optional and the '-' prefix is optional. The options are:")
 usage_list+=("")
+usage_list+=("Build target OS: Use '-os <value>' (handled by the common build framework) to specify the")
+usage_list+=("    target OS. Common values: linux (default on Linux), osx (default on macOS), android,")
+usage_list+=("    ios, iossimulator, tvos, tvossimulator, maccatalyst, browser, wasi.")
+usage_list+=("    For mobile/device targets (android, ios, iossimulator, tvos, tvossimulator), this script")
+usage_list+=("    automatically skips building native test components.")
+usage_list+=("")
 usage_list+=("-rebuild - Clean up all test artifacts prior to building tests.")
 usage_list+=("-skiprestorepackages - Skip package restore.")
 usage_list+=("-skipmanaged - Skip the managed tests build.")
@@ -154,12 +160,13 @@ usage_list+=("-allTargets - Build managed tests for all target platforms (includ
 usage_list+=("")
 usage_list+=("-runtests - Run tests after building them.")
 usage_list+=("-mono, -excludemonofailures - Build the tests for the Mono runtime honoring mono-specific issues.")
+usage_list+=("-coreclr - Build tests targeting the CoreCLR runtime (default; opposite of -mono/-excludemonofailures).")
 usage_list+=("-mono_aot - Use Mono AOT mode.")
 usage_list+=("-mono_fullaot - Use Mono Full AOT mode.")
 usage_list+=("")
-usage_list+=("-test:xxx - Only build the specified test project ^(relative or absolute project path under src\tests^).");
-usage_list+=("-dir:xxx - Build all test projects in the given directory ^(relative or absolute directory under src\tests^).");
-usage_list+=("-tree:xxx - Build all test projects in the given subtree ^(relative or absolute directory under src\tests^).");
+usage_list+=("-test:xxx - Only build the specified test project (relative or absolute project path under src/tests).")
+usage_list+=("-dir:xxx - Build all test projects in the given directory (relative or absolute directory under src/tests).")
+usage_list+=("-tree:xxx - Build all test projects in the given subtree (relative or absolute directory under src/tests).")
 usage_list+=("-log:xxx - Base file name to use for log files (used in lab pipelines that build tests in multiple steps to retain logs for each step).")
 usage_list+=("")
 usage_list+=("Any unrecognized arguments will be passed directly to MSBuild.")