Prior studies have often treated small business in Africa as a homogeneous term thus ignoring its constituent categories. Poor infrastructure, unstable political environment, corruption, and financial constraint have been identified as some of the common obstacles facing micro, small, and medium enterprises in developing economies. With reference to Nigeria, there is paucity of information on the role of size in the perception of the above obstacles. Using the number of employees to determine size, this study attempts to bridge the gap by comparing whether there are significant differences in the perception of obstacles across firms of different sizes. The data for this study are a survey of 247 firms from 5 southern states in Nigeria. The author employed Kruskal-Wallis to test the hypotheses formulated. The findings have shown statistically significant differences on the perception of poor infrastructure and financial constraint across firm sizes. It also revealed specific obstacle(s) facing each state in southern Nigeria. The major implications of these results are that relevant authorities will be able to provide more focused interventions.