Markets and improved market access are critical for improving urban incomes, particularly in Africa. Despite this, participation of farmers in domestic and regional markets in southwest Nigeria remains low due to a range of constraints. One of the limiting constraints faced by farmers is linked to poor market access. Determinants of commercialization of urban vegetable farming in southwest Nigeria were analyzed. Two hundred and thirty vegetable farmers were randomly selected from Oyo and Lagos states. Data were analyzed using descriptive statistics and the Tobit model. The Tobit regression indicated that age, farm size, membership in associations, years of education, distance to market, heterogeneity index, cost of fertilizer, cost of chemicals, and decision-making index influenced extent of commercialization. With diminishing land area it would be more prudent to focus on improving productivity. Social capital enhanced commercialization and it becomes necessary to improve farmer business skills.