We investigate how Japanese men aged 60–74 adjust their workforce attachment after beginning to receive a public pension. Men who were employees at 54 gradually move to part‐time work or retire after beginning to receive pension benefits; those who continue working tend to be underemployed. Men self‐employed at 54, however, neither reduce their working hours nor retire, tending to be overemployed. In contrast, US men retire or become part‐timers when they first claim social security; those who continue working are unlikely to be either overemployed or underemployed. Therefore, unlike US men, Japanese men are not choosing the optimal pensionable age and labour hours to maximize their intertemporal utility.