The purpose of this study was to investigate online social comparison and impostor phenomenon (IP) in undergraduate music education students. I employed a sequential explanatory mixed models design to explore the extent to which music education students experienced IP, used Facebook, and engaged in social comparison on Facebook. I explored participants' perceptions of how they engaged in online social comparison in the context of their professional lives. In Phase 1, I surveyed participants to measure impostor phenomenon, Facebook intensity, and Facebook social comparison. Analysis of the descriptive data revealed that 77.8% of participants experienced frequent to intense IP symptoms. Facebook social comparison emerged as the only significant predictor of IP in participants accounting for 13.3% of the variance in CIPS scores. In Phase 2, I conducted focus groups to investigate participants' perceptions of how they engaged in online social comparison as related to their professional identity. The themes that emerged from the qualitative data included: (a) comparing to peers online, (b) using Facebook for professional purposes, (c) psychological effects of online comparison, and (d) withdrawing from social media to avoid adverse effects. Lastly, I integrated the quantitative and qualitative data to expound upon and confirm findings in each phase. The …