Lack of time is the most frequently reported reason for lack of exercise. This study examines how restriction on the number of working hours affects individuals’ exercise decision. A structural model is constructed to describe the simultaneous decisions of employment and physical activity in the presence of working hour restriction. Using data from the 1992 Health and Retirement Study, this study finds that the working hour restriction is partly responsible for the physical inactivity among older American workers. When the working hour restriction is binding from below, an increase in the number of hours required on the job considerably reduces the probability of engaging in frequent exercise. The results imply that partial relaxation of working hour restrictions may be considered to promote frequent exercise.