This study explored the association between socioeconomic indices and plasma fibrinogen levels in Japanese male and female workers. Occupational category (white-collar vs. blue-collar) and position (manager vs. non-manager) were examined as relevant socioeconomic indices. The study population was a total of 1677 male and 1747 female workers aged 65 and younger taken from the Jichi Medical School Cohort study, a multicenter study designed to explore cardiovascular risk factors in the Japanese population. The association between socioeconomic indices and plasma fibrinogen levels was examined after taking into account several variables such as age, educational attainment, job strain, alcohol consumption, and smoking status and (for women) menopause status. Male white-collar workers had significantly lower fibrinogen levels than blue-collar workers. However, no significant association was found between occupational position and plasma fibrinogen for men. Occupational category interacted with occupational position for women. Among white-collar women, those in non-managerial positions showed higher levels of fibrinogen than those in managerial positions; among blue-collar women, there was no such difference. The association of occupational category and position on fibrinogen levels varied as a function of gender, implying that gender-specific socioeconomic differences could exist in cardiovascular risks in Japanese workers.