The research sought to investigate the significance of trends in annual rainfall in the 45 weather stations across Nigeria, using rainfall data obtained from the Nigerian Meteorological Agency (NiMet) spanning a time interval of 35 years (1981-2015). The research tends to show the pattern of rainfall in other to plan alternative resources capabilities in Nigeria. This will help policy makers to plan towards sustainability in Agriculture, Hydro etc. as an alternative to boost economy in Nigeria. The study thereby identifies data points which were statistically aggregated into their relevant agro-ecological zones in the country. Parametric (Z test) and non-parametric (i.e. Mankandall Test) procedures were then employed to test for the significance of the trends. The study analyses in computing the change points in the rainfall values as well as the magnitude of the changes. The results of both the parametric and non-parametric tests, at the 1% level of significance, indicated upward trends in annual rainfall, significant at the 1% level, over the Swamp, Guinea, Sudan and Sahel agro-ecological zones of Nigeria. Additionally, over these zones annual rainfall during the period under review (1983-2015), increased from 2140 to 2866 mm (with a 100% confidence level), 1341 to 1436 mm (with a 96% confidence level), 861 to 1097 mm (with a 100% confidence level), 480 to 665 mm (with a 100% confidence level), respectively. However, the tropical region showed no significant trend in annual rainfall at the 1% level which invariably reflected in the finding that there is no significant change in annual rainfall in this region. Accordingly, over this region annual rainfall, during the period under review, remained at 1,608 mm. It is based on these findings that the subsequent assessment and discussions vis-àvis implications of the results for the zones are underpinned.