Theoretically, population growth is believed to increase greenhouse gas emissions, particularly CO₂ emissions through the increase in human activities. Accordingly, this study aimed to investigate this assertion in Nigeria using an autoregressive distributed lag model covering periods from 1971-2000, 1971-2005, and 1971-2010 recursively. The results indicated that population was not a determinant of CO₂ emissions in all the three periods in the long run. However, economic growth was found to be the only long-run CO₂ emissions determining factor within the studied periods. However, in the short run, virtually all the explanatory variables and their lags, that is, population growth, economic growth, and energy consumption, were significant in determining CO₂ emissions. The findings suggested that population growth, which is the focal point of the study, could only determine CO₂ emissions in the short run. Therefore, population checking measures could be a short-run effective measure to lower the emissions level. Also, further research should be conducted on how to effectively and efficiently manage the population growth–CO₂ emissions relationship.