In light of the rising percentage of people consuming news from social media as opposed to traditional television, radio, or print or digital newspapers, how individuals decide to trust what they read online is growing more important. As these social networking sites and microblogs provide users with more information than ever, credibility serves as an information filter. This study used an online survey of young adults to compare the perceived credibility of two different types of news outlets on Twitter, mainstream and new media, using individual tweets from common mainstream and new media sources. The source of the tweet, either mainstream or new media, served as the independent variable and was manipulated to measure the perceived message and messenger credibility of the tweet, which served as the dependent variable. Results showed that source had a significant effect on the perceived message and messenger credibility of a tweet such that mainstream sources were considered more credible than new media sources. It also showed that media skepticism had a significant effect on perceived message and messenger credibility, while political cynicism produced no significant effects. Results suggest that mainstream news organizations are still considered more credible than new media organizations on Twitter, even among groups reportedly skeptical of mainstream media.