This paper studies tax competition in an economic geography model that allows for agglomeration economies with trade costs and heterogeneous firms. We find that the Nash equilibrium involves the large country charging a higher tax than the small nation, with this rate being too low from a social point of view. Lower trade costs lead to an intensification of competition, a drop in Nash tax rates, and a narrowing of the gap. Since large, productive firms are naturally more sensitive to tax differences in our model, large firms are the crux of tax competition in our model. This also means that tax competition has consequences for the average productivity of the big and small nations‟ industry; by lowering tax rates, the small nation can attract high-productivity firms.