BACKGROUND: Childhood cancer survivors are at high risk of chronic health conditions. We aimed to explore future long-term sickness absence and disability pension in young adult childhood cancer survivors and matched references. METHODS: We performed a prospective cohort study using microdata from five Swedish nationwide registers. Among all individuals born 1976-1998 and living in Sweden, we included 3632 childhood cancer survivors and 17,468 matched references that could be followed-up for 15, 10, or 5 years, respectively. A group-based trajectory model was applied to identify trajectories of mean annual sickness absence and/or disability pension days (SADP) in each sub-cohort, with 95% confidence intervals (CI). Potential risk factors for trajectory belonging were explored using χ2 test and multinomial logistic regression. RESULTS: Most young adult childhood cancer survivors (90.2-96.5%) and references (97.4-98.8%) followed a No SADP trajectory. A larger proportion of childhood cancer survivors than references followed a Moderate (33-102 days/year) or High (115-260 days/year) SADP trajectory (15-year follow-up cohorts: Moderate 4.6% versus 1.2%; High 5.1% versus 1.5%). Childhood cancer survivors of central nervous system (CNS) tumors were at higher risk of the High SADP trajectory than childhood cancer survivors of hematological or non-CNS solid tumors (hematological versus CNS: odds ratio = 2.30, 95% CI 1.23-4.30; hematological versus non-CNS: odds ratio = 0.32, 95% CI 0.13-0.79). CONCLUSIONS: Although most young adult childhood cancer survivors had no SADP during follow-up, 9.7% experienced moderate or high numbers of SADP days/year throughout the 15-year follow-up; compared to 2.7% among references. CNS tumor survivors were at particular risk of SADP long-term and need extra attention in their future work prospect.