This study examined longitudinal associations between parenthood-related factors and physical activity from young adulthood to midlife over a 19-year follow-up period. Participants (n=761) at the ongoing Cardiovascular Risk in Young Finns Study responded to a self-report questionnaire in their adulthood (in 1992, 2001, 2007 and 2011). Participants were classified as meeting or not meeting an aerobic physical activity recommendation. Parenthood related factors included the age of having their first child, as well as the number and age of the children. Analyses of Generalized Estimation Equations were performed and adjusted for several demographic and health-related covariates. Both mothers and fathers with children under six years were less likely to be involved in physical activity than participants without children. However, meeting the aerobic physical activity recommendations did not differ between parents with a youngest child who was six years old or older as compared to the childless participants. The older the youngest child was, the more likely the parents were to be physically active. Participants who became a parent relatively late, at the age of 30 or older, seemed less likely to meet the aerobic physical activity recommendation during follow-up than those who had their first child at the age of 26-29. The results indicate that parenthood does not seem to have a long-lasting negative impact on adults’ physical activity, and the individuals reached a similar level of physical activity in midlife than they had before parenthood.