Millions of young girls in Nigeria have continued to suffer the negative consequences of early marriage such as discontinuation of education and restricting them from achieving their full potential. Successive Nigerian governments have therefore deployed different strategies over the years to mitigate the practice, particularly in the northern part of the country. This study analysed the changes in the pattern of child marriage across space-time in Nigeria using a dataset obtained from the Nigeria Demographic and Health Survey conducted between 2003 and 2018 at a consecutive interval of 5 years. A Bayesian spatio-temporal random effect model with inference based on integrated nested laplace approximation was considered. Whereas the findings demonstrate a reduction in the practice of child marriage over time everywhere in the country, the prevalence remains highest in States such as Kogi, Niger, Federal Capital Territory Abuja, Taraba, and Kaduna, all in the northern part of the country despite the policies, program and interventions by international organisations, Child Right Acts, and Non-governmental organisations. Over the fifteen years, only slight changes were recorded in the Southwest region. Furthermore, higher levels of education, urban residency, household wealth, being a Yoruba, or belonging to a Christian religious group were found to lower the chances of child marriage. State-specific strategic planning would be useful in deploying suitable local solutions to reduce child marriage in Nigeria.