The study examined the relative economic efficiency of large and small poultry farms in southwestern Nigeria. Results from the profit function without a dummy showed that the coefficient of labour wage rate, feeds and drugs are negative while for fixed cost and farm size turned up to be positive. The profit function and all the explanatory variables significantly affected the profit level. The test of relative economic efficiency between the groups is in favour of the large farms. The elasticities of production showed that the sum of the elasticities is less than one, thus characterized by decreasing returns to scale.