diff --git a/bin/install_app_store b/bin/install_app_store
index e62b14e..c0dfaa7 100755
--- a/bin/install_app_store
+++ b/bin/install_app_store
@@ -9,6 +9,7 @@ IFS=$'\n\t'
 SCRIPT_PATH="$MAC_OS_CONFIG_PATH/bin/install_app_store"
 
 if [[ -x "$SCRIPT_PATH" ]]; then
+  check_mas_install
   "$SCRIPT_PATH"
 else
   printf "WARNING: App Store install script does not exist or is not executable.\n"
diff --git a/lib/utilities.sh b/lib/utilities.sh
index 48a50a5..0cb44e1 100644
--- a/lib/utilities.sh
+++ b/lib/utilities.sh
@@ -95,6 +95,17 @@ get_install_root() {
 }
 export -f get_install_root
 
+# Checks Mac App Store (mas) CLI has been installed and exits if otherwise.
+# Parameters: None.
+check_mas_install() {
+  if ! command -v mas > /dev/null; then
+    printf "%s\n" "ERROR: Mac App Store (mas) CLI can't be found."
+    printf "%s\n" "       Please ensure Homebrew and mas (i.e. brew install mas) have been installed."
+    exit 1
+  fi
+}
+export -f check_mas_install
+
 # Configures shell for new machines and ensures PATH is properly configured for running scripts.
 # Parameters: None.
 configure_environment() {