This study investigates the impact of female concentration on the implementation of parental leave policy by Japanese employers. Specifically, I examine how female ratio and the proportion of married women within firms affect Japanese employers' decisions about providing parental leave for their employees. I discuss how these employer characteristics are likely to be associated with the provision of family assistance based on theories of organizational behavior and test these hypotheses using data from 1779 business establishments in Japan. Findings indicate that firms with predominantly female workforces were not necessarily more likely to adopt parental leave. Surprisingly, the proportion of married women at the workplace exerted a powerful negative impact on employer adoption of parental leave, and this negative effect was significant across all levels of industrial female concentration. Results also show that the presence of a climate at work that discriminates against women tends to prevent the provision of parental leave. Interestingly, the proportion of women managers in a firm reduced the likelihood that parental leave is adopted by employers of large firms and heavily female industry.