Two experiments tested whether exposure to partisan conflict-framed news polarizes news consumers along party lines. Partisan self-categorization and motivated reasoning were examined as potential mediators of this effect. In two samples, path analyses showed that Democrats and Republicans exposed to partisan conflict-framed news adopted more polarized opinions on a disputed issue. This polarization effect was consistently mediated by perceived argument validity, an indicator of motivated reasoning; increased partisan self-categorization also mediated the effect, though less reliably and consistently. Thus, the present study adds to the literature on polarization by providing experimental evidence that exposure to conflict-framed news may contribute to partisan polarization. Theoretical and practical implications are discussed.