This paper examines the role of poverty in Nigeria's fertility transition using household survey data from Nigeria - Kaduna and Lagos states - of which 2425 respondents were sampled. In Nigeria, much attention has not been paid to the link between poverty and fertility preferences. This paper is aimed at filling this research gap. It uses univariate and bivariate analyses in examining the proximate determinants of fertility dynamics with particular emphasis on the role of income poverty. One of the variants of fertility preferences used is the number of children respondents desired after their experiences with economic hardship- declining standard of living. Evidence from the study shows that majority of the respondents from the northern part desired more children than their southern counterparts, which partly conforms to spatial distribution of poverty. Due to higher incidence of poverty among rural dwellers, they now prefer lower fertility formation. In the absence of poverty, however, fertility rate is lower in urban areas due to education and exposure to family planning services. Generally, respondents who agreed that poverty had affected their economic expectations and attitude about large family size and now desire lower fertility rate compared to those that were indifferent or held opposing views. Other proximate determinants of fertility dynamics are women education, religion, spousal communication and spousal approval of contraceptive usage, male dominance, spousal age difference, polygyny and early marriages. In addition to investing in basic education and health care delivery that offer substantial synergies for empowerment and economic opportunities thereby promoting lasting growth and reducing poverty, the following also deserves attention. Special family planning programmes should be targeted at men, particularly in the northern part of the country. Promotion of high level female education because of its synergy with better living conditions contraceptive usage, spousal communication, and low fertility preference. Promotion of peer-wise marital union, monogamy, and late marriages is also important. The need for committed and pro-active promotion of a culture of low fertility preference using the above methods, among others, is fundamental to maintaining this transition to low fertility. Otherwise, the emergence of better economic conditions in the future would reverse the fertility trend.