The lack of women in Science, Technology, Engineering, and Mathematics (STEM) careers is a multifaceted problem, and there may be various levers for change (e.g., managers’ attitudes). Whereas most previous studies have focused on educational aspects, we targeted later career stages: We measured managers’ gender role attitudes because managers can be a source of support or discrimination. In fact, women in STEM fields report less support and more discrimination than STEM men or non-STEM women do. Using a large and representative data set from the Socio-Economic Panel (SOEP) in Germany, we compared traditional gender role attitudes in STEM versus non-STEM fields with ordered probit regressions and a multiverse analysis. We found that male, older, non-managerial, and non-STEM employees had more traditional gender role attitudes than others. Additionally, we found a gender gap: For men, older employees had more traditional gender role attitudes; for women, age did not matter, but female managers had less traditional gender role attitudes than non-managers. Reasons for this trend might be selection (e.g., women with traditional attitudes might abandon their careers earlier) or socialisation (e.g., female managers’ attitudes may change in male-dominated environments). Implications for women’s careers are discussed.