Maternal parenting stress during childhood may have important influences on offspring internalizing and externalizing behaviors during adolescence in unmarried households, but it is unclear whether effects differ across different trajectory patterns of maternal parenting stress and for native-born vs. immigrant families. Using data from the Future of Families and Child Wellbeing Study, we identified trajectory patterns of maternal parenting stress from ages 1-9 years using semi-parametric group-based trajectory modeling. We used negative binomial regression models to estimate associations between maternal parenting stress trajectories and adolescent behavioral symptoms at age fifteen. Five maternal parenting stress trajectory groups were identified among the 1982 unmarried families included in this study, representing consistently low (9.2 %), consistently mild (54.2 %), moderate and decreasing (14.4 %), moderate and increasing (16.0 %) and consistently high (6.2 %) levels of maternal parenting stress. For adolescent internalizing symptoms, all maternal parenting stress trajectory groups exhibited higher symptoms compared to the consistently low group: IRR for consistently mild: 1.21 (95 % CI: 0.98-1.56); IRR for moderate/decreasing: 1.34 (95 % CI: 1.04-1.74); IRR for moderate/increasing: 1.62 (95 % CI: 1.28-2.13); and IRR for consistently high: 1.74 (95 % CI = 1.29-2.41). Similar results were observed for adolescent externalizing symptoms. Stronger effects of maternal parenting stress trajectories on adolescent externalizing symptoms were observed among native-born vs. immigrant families. Differential attrition and same-source bias may lead to under- or over-estimation of the associations of interest. Interventions targeting unmarried families with elevated maternal parenting stress during childhood may reduce behavioral symptoms in adolescence.