Student success in online learning is strongly affected by the learner's social presence. There is evidence that not all students benefit from the online learning environment, as it limits social interaction between the students. The purpose of this study was to examine the impact of Twitter, a social network application, on online class engagement. The guiding theories of this study were the constructivist and connectivist theories. The research question examined the effect of Twitter usage on academic performance, as measured by course grade, and engagement level. This quasi-experimental posttest design study used a convenience sample of 116 students at an urban community college. The treatment group (n = 44) and comparison group (n = 72) students were enrolled in an online classroom. The treatment group also integrated the non-formal use of Twitter. The survey data were analyzed using multiple linear regression. The main independent variables, quantity of tweets (r = 0.20, p = 0.20) and quality of tweets (r = 0.12 p = 0.43), were not statistically correlated with academic performance. Differences between the groups on academic performance were not statistically significant (t (72.75) = 1.38, p = 0.17). However, students in the treatment group who self-reported that the tweets increased their level of engagement, also self-reported a higher final grade average (M = 88.18, SD = 9.405). Implications for positive social change include information that can be used to inform instructors for creating an ungraded, informal environment which will make their online classes more engaging, increase the dialogue between the students and the instructor, and ultimately improve the learners' success in online classes. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]