Human fertility is a function of a variety of factors classified into proximate (direct) and distal (indirect) factors. A proper understanding of these factors is of paramount importance in tackling the problem of uncontrolled fertility, which commands enormous positive and negative consequences. This paper therefore isolated the determinants of population growth in Nigeria as caused by uncontrolled fertility, and ascertained the relationship between the population growth offshoot and economic growth in Nigeria. These were achieved by using data downloaded from the World Bank databank for a period of 51 years (1961-2011). Findings determined that high fertility and birth rate contributes positively to high population growth while further findings revealed that high population growth rate in Nigeria exerts negative consequences on the Nigeria’s economy. These negative consequences can be appreciated by high poverty, inadequate housing, poor sanitation, low standard of living, high unemployment rate and inflation, high pressures on existing infrastructural facilities etc.