This study explored the efect of workplace psychosocial factors (job demand, job control, and workplace social support) on dual-earner couples in Japan having additional children, using a prospective study design. We conducted a 2-year prospective cohort study with 103 dual-earner couples with preschool children in Japan, as part of the Tokyo Work-Family Interface Study II. We used multivariable logistic regression analyses to evaluate the prospective association of job strain (categorized into low-strain job, active job, passive job, and strain job groups) and workplace social support (high and low) with couples having additional children during the follow-up period, adjusting for age, for men and women separately. Men in the active job group (i.e., with high job demands and high job control) had a signiicantly higher odds ratio (OR) of having additional children during the follow-up period, after controlling for age (OR 9.07, 95% conidence interval: 1.27-64.85). No signiicant association between any workplace psychosocial factor and having additional children was conirmed among women. Having an active job may have a positive inluence on having additional children among men in dual-earner couples.