This study explored how middle-aged workers’ career trajectory patterns were associated with their financial security later in life. Grounded by a life course perspective, we approached their career trajectories by considering a ‘human agency within structure’ framework. We explored sequences of employment status, starting with their lifetime main job to subsequent jobs after contractual retirement, using data from 1,010 middle-aged adults in Seoul, South Korea. The sequence analysis identified six career trajectory patterns. Stable career patterns included the Permanent to permanenttrajectory as well as the Permanent to self-employmenttrajectory and these were most common among males with higher education degrees, higher earnings and better career alignment. Unstable career patterns such as the Temporary to temporary trajectory, the Permanent to temporary trajectory or the Churning trajectory were most common among those who were female, had lower levels of education lower earnings or had retired involuntarily. Further results showed that unstable career patterns were associated with lower levels of monthly earnings and total assets post–contractual retirement. Individuals with unstable career patterns were also less likely to be financially prepared for retirement. We suggest individualising education programmes for retirement preparation based on various career trajectories and demographic attributes to aid middle-aged adults in preparing for financial security later in life.