AbstractMen extend their employment beyond pensionable age more often than women, but the factors that contribute to this sex difference are unknown. This study aimed to examine sex differences in extending employment and the contribution of sociodemographic, work- and health-related factors to these differences. Participants of this prospective cohort study were 4,263 public sector employees from Finland who reached their individual pensionable date between 2014 and 2019 and responded to a survey on work- and non-work-related issues before that date. Extended employment was defined as continuing working for over six months beyond the individual pensionable date. We used mediation analysis to examine the contribution of explanatory factors to the association between sex and extended employment. Of the participants, 29% extended employment beyond the pensionable date. Men had a 1.29-fold (95% confidence interval 1.11–1.49) higher probability of extending employment compared with women. Men had a higher prevalence of factors that increase the likelihood of extended employment than women (such as spouse working full-time, no part-time retirement, low job strain, high work time control, and lack of pain) and this mediated the association of sex with extended employment by up to 83%. In conclusion, men were more likely to extend their employment beyond pensionable age than women. This difference was largely explained by men being more likely to have a full-time working spouse, low job strain, high work time control, no pain, and not being on part-time retirement.