This paper theoretically examines new sources of trade gains arising from the interaction of (i) IO network and (ii) pro-competitive effects. To this end, we develop a general equilibrium model and derive an endogenous markup under oligopolistic competition with an IO network. Our markup has an intuitive closed-form function and nests the markup of Atkeson and Burstein (2008) as a special case. We use this model to revisit the problem considered by Edmond et al. (2015). We find that the IO network amplifies the gains associated with the reduction in misallocation and that the gains from trade are more than twice as large as in the absence of the IO network. Furthermore, we find that trade gains are even larger under the assumption of complementarity of intermediate goods.