This study is based on three Demographic and Health Surveys conducted in Nigeria, in 2003, 2008, and 2013. The study was undertaken against the background of a persistently high rate of population growth in Nigeria, caused primarily by a high fertility rate that has shown few signs of decline. The United Nations medium population projection for Nigeria shows an increase from 282 million in 2015 to about 400 million by 2050, even with an assumed substantial decline in fertility. The present analysis explores the components and some of the covariates of fertility in Nigeria, recent trends, and potential future changes. One objective is to assess the extent to which various components of reproduction and their changes in Nigeria since 2003 can be explained at the macro level of the country’s 37 states as well as at the individual level. Trends in age at marriage, reproductive preferences, contraceptive use, teenage fertility, child mortality, and total fertility are described. The covariates of these reproductive components highlight the importance of women’s education, child mortality, monogamy, religion, and exposure to television and radio. Residence in the South of Nigeria is consistently associated with lower fertility. The most important determinants of fertility decline in Nigeria are increases in women’s education and decreases in child mortality. However, while declines in child mortality in recent years have been considerable, they have not yet translated into substantial declines in fertility, and increases in women’s education have been very slow.