The “filter bubble” has been a heated discussion topic since several years ago. In addition to possible algorithmic contribution to this phenomenon, people’s selective exposure tendency may be another primary cause of the “filter bubble” on social media. Prior research indicates that, under the influence of selective exposure tendency, people tend to perceive pro-attitudinal news as more credible than counter-attitudinal news, with strong partisans more likely to be affected. The proposed thesis seeks to examine whether the perceived credibility of a news source and story on social media is influenced by selective exposure and strength of partisanship. Through an experimental study via Amazon’s Mechanical Turk, 468 participants chose or were assigned to read an ostensible news story from a social media feed with the news source and ideological slant varied between participants. The results showed that people reported higher perceived source and story credibility when the source and stories were pro-attitudinal (consistent with their political ideology) as opposed to counter-attitudinal, regardless of participants’ age, race, perceived credibility of news from social media, in general, and strength of partisanship. However, contrary to the hypotheses, selective exposure behavior (i.e., choosing a preferred news source before reading a news story) did not affect credibility perceptions when participants read counter-attitudinal news from a pro-attitudinal source. Last, strength of partisanship did not moderate the influence of selective exposure on credibility perceptions. In sum, this study suggests that although selective exposure tendency may affect people’s credibility perceptions and contribute to “filter bubbles,” the impact of selective exposure behavior may be overestimated in terms of perceived source and story credibility of news on social media.