Societies which rely upon agriculture for their livelihood may face the perils of climate change, especially developing countries in the tropics and subtropics such as Nigeria in which some of the food crops are already close their peak temperature tolerance. This study was to evaluate root and tuber crops yield under the changing climatic conditions in Kwara State, located in the Guinea savannah Zone of Nigeria. Climate and crop yield data (cassava and yam) covering a period of twenty years (1995-2014) were collected from Nigerian Meteorology Agency (NIMET), Abuja and Kwara State Agricultural and Rural Development Office, Ilorin respectively. The data were analysed using trend analysis, Johansen’s multivariate co-integration test and error correction modelling. The results show an increased in annual rainfall of about 12.42 mm/year from 1995 to 2014 with minimum temperature increasing at a faster rate compared to maximum temperature. The Augmented Dickey-Fuller test showed that climate variables were stationary at levels whiles cassava and yam yield were stationary at first differencing. The co-integration analysis and Error correction model estimates indicate that, there is at least one long-run relationship between yam yield, rainfall and temperature, whereas cassava yield, rainfall and temperature react to at least three long term equilibrium relationships. The study revealed that yam yield is affected positively by rainfall and temperature. Also, output of cassava is significantly affected by rainfall and with the expected positive sign. The study primary concludes that root and tuber crop production is climate dependent, and that the yield of yam and cassava are affected positively by rainfall and temperature.