Mary Wilshire's comic book career developed first in underground comix. Mary had grown up as a fan of Mad magazine and newspaper comics, and was influenced by Jack Davis, Stan Drake and Alex Kotzky. Wilshire's first work for Marvel Comics came around 1980, when she contributed to Crazy. Later, Larry Hama asked her to take over the drawing of 'Red Sonja'.
Wilshire's other work for Marvel included 'Power Pack', 'Ka-Zar', 'Spider-Man' and 'Barbie'. She also drew two monthly pages for National Geographic's children's magazine, National Geographic World, called 'The Amazing Travel Bureau'.