She held a PhD in zoology and spent her professional career working as a researcher at the United States Public Health Service and the University of California, Berkeley.

When Sumner Brooks died in 1948, Matilda was left with a lab and some small grants at Berkeley but no salary, the result of the university's anti-nepotism policy, which had barred her from a paying job when her husband had accepted his faculty post.

In Matilda M. Brooks v. Commissioner of Internal Revenue, she argued that even though she couldn't hope to earn a living from publishing scientific papers alone, she would profit professionally by gathering materials and conferring with peers to preserve her academic reputation during European travel.

In 1959 Justice Stanley M. Barnes held in favor of Brooks and reversed the lower court decision, writing: "It is difficult in view of mankind’s almost universal drive for monetary reward alone to recognize that petitioner was required to spend many thousands of dollars to retain the position paying her but $500 per annum.

The education of women has progressed a long way from the time when they were allowed to sit out of sight behind curtains to listen to the words of wisdom which proceeded from the mouths of men instructors...