This paper analyzes the reciprocal relationship between occupational gender segregation and occupational part-time work in West Germany over time. Based on a unique occupational panel dataset covering 254 occupations between 1976 and 2010, we apply static, dynamic, and Arellano-Bond panel models to account for reverse causality and endogeneity. Results indicate that trends in occupational part-time rates and gender ratios mutually reinforce each other but not in the same manner. Part-time work in occupations increases once more women start working in these occupations. Occupational part-time ratios are mainly driven by married women and mothers; women's education level only plays a minor role. Vice versa, the gender composition of occupations is likewise affected by changing working-time arrangements, at least in the short run, but it is mainly driven by previous levels of occupational gender segregation.