Having and raising children can be a source of joy for parents. However, the transition to parenthood is associated with a certain degree of strain and stress, and couple relationship quality often declines during the transition. Coparenting, the shared responsibility of childrearing, benefits both parents and children and is an important aspect of the transition to parenthood. In this quasi-experimental study, we aimed to develop a couple education program in Japan that focuses on coparenting among couples expecting their first child. Twenty-one healthy couples voluntarily participated in the intervention group (n = 16) or the control group (n = 5). Couples in each group could voluntarily participate in standard childbirth education classes. The intervention was a couple education program designed to enhance coparenting and consisted of two interactive classes, including discussions within each couple and watching a short video showing an example of childrearing. We collected outcome measures on childrearing, couple relationship, parental mental health, and child adjustment at 1 month and 3 months after childbirth. Multiple regression analysis was performed and showed positive effects of the intervention on childrearing and child adjustment. Being in the intervention group had a significant positive effect on Coparenting Support scores at 1 month after childbirth (β = 0.457, p < 0.003, R2 = 0.187) and Soothability scores for child adjustment at 3 months after childbirth (β =0.429, p < 0.006, R2 = 0.157). In conclusion, we have developed the prenatal education program focusing on coparenting for Japanese couples.