Improving farmers’ welfare has been the concern of the government and international donors in sub-Saharan Africa and particularly in Cameroon. Encouraging farmers to adopt agricultural extension services is one of the most important measures implemented to improve the rural farmers’ welfare situation. Thus, the main aim of our study is to assess the impact of the adoption of agricultural extension services on the welfare (food security) of smallholder rural farmers in the Centre region of Cameroon. Our study employs the endogenous switching regression model to account for both selection and endogeneity bias on survey data obtained from two divisions in the Centre region of Cameroon. Using Household Dietary Diversity Score (HDDS) as a measure of our food security access indicator, results suggest that adoption of agricultural extension services significantly reduces the HDDS of farmers’ households by 0.267 points at 5 percent significance level. This result demonstrates that adopting agricultural extension services doesn’t improve the diversity of nutritional intake by rural farm households thereby suggesting the benefits obtained from income does not always lead to the consumption of diverse nutritional food. Given that food security has no standard measurement, extension services adoption could, however, improve other aspects of food security.