Welfare implication of agricultural commercialization in developing countries is not clear. Particularly not clear is its effect on household food security. Using panel data collected from smallholder farmers in Kenya, we analyze the impact of agricultural commercialization on household food security by fitting endogenous switching regression model in a correlated random effects framework. The results show that agricultural commercialization significantly improves household food security. Food security probability of commercialized and non-commercialized households was 62% and 32%, respectively. This 30% food security gap between the two groups of households could be reduced by 39 percentage points (12% gap) if non-commercialized households could be as efficient as commercialized household in their resource use. The other 61% percentage points (18% gap) emanated from differences in resource amounts between commercialized and non-commercialized households. The implication of these findings is that policies that stimulate and enhance agricultural commercialization are critical in improving household food security. Acknowledgement : This study was supported by the Australian Centre for International Agricultural Research (ACIAR) and Australian International Food Security Research Centre (AIFSRC) through International Maize and Wheat Improvement Center (CIMMYT) led Sustainable Intensification of Maize-Legume Cropping Systems in Eastern and Southern Africa (SIMLESA) program, and Adoption Pathways Project. The views expressed here are those of authors and do not necessarily reflect the views of the donor or authors institution. The usual disclaimer applies