Studies have focused on the effect of short birth spacing on childhood mortality, yet very little attention has been paid to the possibility of an inverse relationship such that child mortality might also positively or negatively affect birth spacing. In Nigeria, where both fertility and child mortality are high, this inverse relationship is a possible reason for the country’s high fertility. The objective of this study was to examine the effect of child death on time to birth of the next child. Data were drawn from the 2013 Nigerian Demographic Health Survey. The study sample comprised 188,986 live births born to women aged 15–49 years within the five years preceding the survey. A multivariate Cox proportional hazard regression model was fitted to the data, and hazard ratios with 95% confidence intervals calculated. More than half of the mothers (68%) already had a next birth by 36 months after the death of the index child. Controlling for other covariates, the Cox regression model showed that the likelihood of next birth was higher when the index child had died compared with when the index child survived (HR: 2.21; CI: 2.03–2.41). Sub-group analysis by geo-political regions in Nigeria showed that in all regions there was a higher likelihood of having a next birth following the death of a preceding child. Death of the index child was found to be a major factor that shortens the length of birth intervals in Nigeria. It is therefore important that the Government of Nigeria intensifies efforts aimed at reducing infant mortality and encouraging adequate birth spacing.