We investigate how vertical relatedness between business segments of firms affects capital allocation within internal capital markets. Using a battery of tests including exogenous import tariff reductions, we show that investments flow toward segments with better investment opportunities in firms with significant vertical relatedness between segments. This benefit of vertical relatedness is more pronounced in economic environments prone to information problems and in imperfectly competitive industries. Firms with significant inter-segment vertical relatedness also exhibit superior productivity and operating profitability. Overall, we show that superior capital allocation is a channel through which vertical integration impacts real outcomes of firms.