Although the relationship between road improvement and agricultural development has long been studied, there are few studies that analyze the effect of road quality on smallholder farmers’ access to agricultural markets. This empirical study of smallholder potato producers in (South Kinangop) rural Kenya tries to fill this gap. Results of partial and multivariate analyses indicate that road quality and increase in market accessibility have significant effect on fertiliser use. Similarly, the use of fertiliser has a strong and significant effect on potato yield. These findings demonstrate that improvement in road quality influences potato yield through increased fertiliser use. Farmers in areas served by high quality roads applied more fertiliser per acre than those in areas served by medium and low quality roads. These findings suggest that improving the quality of rural roads can induce farmers to invest more on fertiliser thus creating the basis for growth in agricultural productivity and rural incomes. The study concludes that better quality roads enhance farmers’ access to markets and has major implications for developing countries.