The study uses a country-wide data from a stratified sample of 600 rice farmers to assess NERICA adoption rates and the causal effect of NERICA adoption on rice yields and income. It reveals that the observed sample adoption rate does not consistently estimate the true population adoption rate even if the sample is randomly selected. Consequently, it uses the counterfactual outcomes framework to estimate the true population adoption rate which corresponds to what is defined in the modern policy evaluation literature as the average treatment effect (ATE). The ATE estimate shows that the NERICA adoption rate could have been 83% instead of the observed 40% sample estimate provided exposure to NERICA was complete in 2006 or before. This shows an adoption gap of 43%, which represents a very high unmet demand for NERICA in The Gambia. Moreover, the results of the causal effects of NERICA adoption on rice yields and income based on observed sample estimates show significant differences between NERICA adopters and non-adopters. However, since the observed estimates could be attributed to differences in socio-demographic and environmental characteristics of adopters and non-adopters, they may not have any causal interpretation of NERICA adoption on the variables of interest. Indeed, the importance of some socio-demographic and environmental characteristics variable in explaining the differences in rice yields and income between NERICA adopters and non-adopters was confirmed by the data analysis. Hence, the study uses the counterfactual outcome framework to control for such differences. The results of the framework based on ATE estimates show in general significant estimates of NERICA adoption on rice yields and income. However, since adoption is a choice variable, the ATE estimates cannot be given a causal interpretation. Therefore, the study proceeds with the LATE estimates, the impact parameter which has a causal interpretation under this circumstance. The LATE estimates show that NERICA adoption significantly increases average rice yields and daily income of small-scale rice farmers by 146 kg/ha and D10.16 respectively.