ObjectiveThe purpose of this study was to investigate the association between depressive symptoms and second primary cancer (SPC) in U.S. cancer survivors. MethodsCancer survivors from the 2005–2018 National Health and Nutrition Examination Survey (NHANES) were included in this cross-sectional study, and depressive symptoms were defined by the Patient Health Questionnaire 9 (PHQ-9). The association between depressive symptoms and SPC was assessed via multiple logistic regression, restricted cubic spline (RCS), sensitivity, and subgroup analyses. ResultsThis study involved 2315 participants representing >15 million noninstitutionalized U.S. residents. Multivariate logistic regression fully adjusted for confounders revealed that cancer survivors with a PHQ-9 score ≥ 10 had a greater risk of developing SPC than those with a PHQ-9 score of 0–4 ([OR] = 1.88, 95% [CI] = 1.20–2.89, p = 0.005). The RCS showed a linear positive correlation between the PHQ-9 score and SPC (p for overall = 0.017). The robustness of this association was subsequently confirmed via multiple interpolation of missing data and different cluster-level methods (namely weighted linear regression) as sensitivity analyses. Furthermore, subgroup analyses confirmed this correlation was stronger in participants with sleep duration <7 h (p for interaction = 0.036). ConclusionModerate to severe depressive symptoms in cancer survivors were associated with an increased risk of developing SPC, especially at <7 h of sleep.