As a PhD student, Valentine realized that there were not many professors who looked like her. From 1973 to 2012, only 66 black American women earned PhDs in physics, compared to 22,172 white men. She became involved with national efforts to improve diversity in physics. She developed the nonprofit African American Women in Physics (AAWIP), which honors the contributions of African American women to physics. She has made efforts to meet and document as many of them as she can. She has worked with the National Society of Black Physicists to increase awareness of underrepresented groups to physics.