Despite growing calls to analyse internal migration as a life‐course trajectory, most studies use the last recorded migration based on a dichotomy between migrants and non‐migrants. Leveraging the maturation of longitudinal surveys and methodological advances, this paper establishes the diversity and complexity of individual migration trajectories and their long‐term association with subjective well‐being. We apply sequence and cluster analysis to the Household, Income and Labour Dynamics in Australia (HILDA) survey data to establish the migration trajectories of millennials from the ages of 15–18 to 27–30 based on the timing, frequency, and direction of migration between regions. We then combine data mining techniques, machine learning algorithms and regression analysis to explore the association between internal migration trajectories and economic and social subjective well‐being (SWB). We find that a full third of young adults are repeat migrants split between return migrants, serial onward migrants, and circular migrants. Repeat migrants often exhibit lower levels of life satisfaction. Successive migrations cumulatively shape life satisfaction, as shown by a negative association between serial onward migration and social SWB. Additionally, return migrants are less satisfied with their economic outcomes, particularly when return migration occurs after two consecutive onward migrations or when return migration occurs early in adulthood. Collectively, these results reveal heterogeneity in migration trajectories that are missed when migration is treated as a one‐off event while suggesting that internal migrants operate a trade‐off between social and economic outcomes over the life course.