Mecyna mustelinalis is a moth in the Crambidae family. It was described by Packard in 1873. It is found in North America, where it has been recorded from Alberta, Arizona, British Columbia, California, Manitoba, Montana, Nevada, Saskatchewan, Utah, Washington and Yukon. The length of the forewings is 12.5–16.5 mm. Adults have been recorded on wing from March to August, with most records from July.