Exposure to conflicting political viewpoints is widely assumed to benefit the citizens of a democratic polity. Nonetheless, the benefits of exposure to heterogeneous political viewpoints have yet to be demonstrated empirically. Drawing on national survey data that tap characteristics of people's political discussion networks, I examine the impact of heterogeneous networks of political discussion on individuals' awareness of legitimate rationales for oppositional viewpoints, on their awareness of rationales for their own viewpoints, and on levels of political tolerance. Finally, utilizing a laboratory experiment manipulating exposure to dissonant and consonant political views, I further substantiate the causal role of cross-cutting exposure in fostering political tolerance.