Background: Mental illness is a leading cause of the disease burden among young people. Poor mental health is linked to childhood adversity such as gender inequality, poverty and low educational attainment. Psycho-social assets in adolescents can moderate these impacts and be strengthened. The aim of this study was to assess the effectiveness of a brief mental health and resilience intervention among disadvantaged young women in urban North India. Methods: We used an uncontrolled repeated measures design to evaluate the effectiveness of the 15-module mental health and resilience curriculum among young women residing in a slum in Dehradun, Uttarakhand. Standardised psychometric assessments were done to assess outcomes of the intervention at three time-points: pre-intervention (T1), post-intervention (T2), and 8-months post-intervention (T3), covering domains of self-efficacy, resilience, anxiety, depression and gender attitudes. Results: Young women completing the intervention (n=106) had all left school before 10th class. A statistically significant improvement in all psychometric measures was found at T2. These improvements were sustained at T3 in the areas of anxiety, depression and gender equality attitudes, while the measures of resilience and self-efficacy had declined to baseline. Conclusions: This intervention delivered by community-based peers among highly disadvantaged young women can lead to sustained improvements in anxiety and depression and attitudes to gender equality. While other studies in LMIC have shown increased adolescent resilience through peer-led curriculums, this study demonstrates improvements in mental health and gender attitudes can endure 8-months post-intervention. This low-cost, brief intervention can improve mental health resiliency and self-efficacy among disadvantaged young people. Further research should explore how to bring sustained improvements in resilience.