Selective exposure research indicates that news consumers tend to seek out attitude-consistent information and avoid attitude-challenging information. This study examines online news credibility and cognitive dissonance as theoretical explanations for partisan selective exposure behavior. After viewing an attitudinally consistent, challenging, or politically balanced online news source, cognitive dissonance, credibility perceptions, and likelihood of selective exposure were measured. Results showed that people judge attitude-consistent and neutral news sources as more credible than attitude-challenging news sources, and although people experience slightly more cognitive dissonance when exposed to attitude-challenging news sources, overall dissonance levels were quite low. These results refute the cognitive dissonance explanation for selective exposure and suggest a new explanation that is based on credibility perceptions rather than psychological discomfort with attitude-challenging information.