An estimated 58,000 women died from pregnancy-related complications in Nigeria in 2015 alone. Family planning (FP) reduces maternal mortality through the prevention of unintended and high-risk pregnancies. Using the Socioecological Framework, this dissertation assessed modern contraceptive method use among women living in six cities in Nigeria: Abuja, Benin, Ibadan, Ilorin, Kaduna, and Zaria. The first study estimated the determinants of modern method use among the women. Data from multiple cross-sectional surveys collected in 2010/2011 were linked to provide information on the intrapersonal, interpersonal, institutional, community, and societal socioecological levels. Multilevel logit models estimated the odds of modern method use among 15,947 women living in 488 clusters. About 21% of the women reported using modern methods. There were statistically significant direct and cross-level interaction associations between the socioecological factors and modern method use. The second study examined the associations between changes in gender-equitable norms and changes in modern method use among the same women followed over time. The analytical sample included 9,933 women living in 480 clusters. Multilevel multinomial models estimated the associations between the change in modern method use and changes in gender-equitable norms towards: wife beating; household decisions; couples’ FP decisions; and FP self-efficacy. The use of modern methods increased from 21% to 32% during the study period. Positive changes in the gender-equitable norms towards household decisions, couples’ FP decisions, and FP self-efficacy were significantly associated with increased probability of modern method adoption and continued use and decreased probability of discontinuation during study period. These findings highlight the need for multilevel interventions to improve modern contraception in urban Nigeria. Such FP interventions should be tailored to the characteristic of the target communities.