Adoption of improved agricultural technologies is crucial to improve land productivity, food security and economic development in low-income countries. In this paper, we examined the determinants of improved maize variety (IMV) adoption and the impact of adoption on land productivity of resource-constrained smallholder maize farmers in a semi-arid region of Ghana. Primary data on 340 respondents were gathered and modelled using an endogenous switching regression econometric model to evaluate the impact and determinants of maize technology adoption among the sampled farmers. From the results, adoption of IMV significantly improved land productivity by 10.7 – 14.1 percent. Furthermore, quantity of labour deployed by the household was found to be a key determinant of both adoption and land productivity, while factors which enhance soil fertility status positively influenced improved variety adoption. The authors make practical policy recommendations to enhance adoption and land productivity to improve food security and income of smallholder farm households.