We examine the effects of the trade liberalization that accompanied China’s WTO accession on the evolution of markups and productivity of Chinese manufacturing firms. Although these two dimensions of performance cannot be separately identified when firm output is measured by revenue, we show that detailed price deflators make it possible to estimate the average effect of industry-level tariff reductions on both dimensions separately. Several novel findings emerge. First, cuts in output tariffs reduce markups, but raise productivity. Second, the procompetitive effects are most important for incumbents, while efficiency gains dominate for new entrants. Third, cuts in input tariffs raise both markups and productivity. We highlight several mechanisms operating in liberalized sectors that help explain our findings in the Chinese context. Liberalized sectors saw an increase in the exit of private firms and more frequent replacement of management in badly performing state-owned firms. Both patterns are likely to reduce agency problems. The initial productivity of new entrants is higher in more open sectors. And while lower input tariffs had only a limited role in increasing access to imported intermediates, they had a strong price-reducing effect, even on domestically produced intermediates.