The search functionality in woocommerce doesn't search by product tags by default.\
This simple plugin adds this functionality to both the admin site and regular search.\
You can search by multiple tags by splitting your search with a comma. For example to search for all products tagged with toys and helicopter enter into the search box: “toys, helicopter” and all products with those tags will be returned in the search.
Tested with Woocommerce 1.5.6, 2.0.7 and 2.1.5
See the
Accompanying blog post for more info.