Background: Husbands and in-laws often control decision-making around fertility due to gendered social norms and practices in India. This can lead to a lack of women’s reproductive control resulting in challenges around contraception use and unintended pregnancy. Objective: To examine women’s decision-making – a key aspect of agency – in family planning and contraceptive use, with young married couples in rural Maharashtra, India and married adolescent girls in Bihar and Uttar Pradesh, India. Methods: Cross-sectional studies were carried out using dyadic young couples data in Maharashtra, India (N=961 Chapter 2; N=1,200 Chapter 3), and married adolescent girls (N=4,893, Chapter 4) in Bihar and Uttar Pradesh, India. Multivariable regressions examined associations between 1) spousal reports of the wife’s involvement in contraceptive decision-making and modern contraceptive use (Chapter 2); 2) marginalizing marital practices (female non-involvement in marital choice, child marriage, dowry, and purdah) with three family planning behavioral outcomes: contraceptive decision-making, communication, and use in marriage (Chapter 3); 3) and in-laws’ fertility pressure and marital family planning communication, contraceptive use, parity, and time until first birth (Chapter 4). Results: Chapter 2 shows that couples where women report they are not involved and men report women are involved, have lower odds of contraceptive use, relative to those with couple agreement on female involvement (adj. RR=0.61, 95% CI 0.45, 0.83). In Chapter 3, women reporting marital choice have higher odds of marital contraceptive communication (AOR 2.08, 95% CI 1.26, 3.44) and modern contraceptive use (AOR 1.73, 95% CI 1.11, 2.71). Chapter 4 shows that in-laws’ fertility pressure was associated with lower parity (adj. β -0.10, 95% CI -0.17, -0.37) and couple communication about family size (AOR 1.77, 95% CI 1.39, 2.26). Conclusions: Findings indicate that women’s decision-making involvement can be important for women’s contraceptive use as well as for their marital communication regarding family planning and fertility discussions. Couple and adolescent focused family planning interventions would benefit from greater focus on women’s agency in marriage including for marital choice and contraceptive use, as well as engagement of male partners in family planning; in pronatal contexts emphasizing on social norm change broadly and targeting parents/in-laws of newly married individuals in a way that does not reinforce their power but focuses on women’s agency.