The widespread adoption of video-conferencing has not only transformed communication at scale, but also increased feelings of Zoom fatigue among workers around the world. Although Zoom fatigue is well-documented, it is still unclear what aspects of video-conferencing contribute to this sense of exhaustion. This paper leveraged theory on computer-mediated communication (CMC) to investigate the causes of Zoom fatigue in an online convenience sample of 9787 participants. We provide empirical evidence that Zoom fatigue is influenced by the dynamics of individuals’ video-conferencing usage and their psychological experience of the meeting. Specifically, our results support Bailenson’s theory of nonverbal overload (2021) that video-conferences are exhausting because maintaining the nonverbal communication cues required in video-based calls (e.g., making eye contact with many people at once) can be draining. We found that people who used video-conferencing more frequently, for longer and with fewer breaks reported more Zoom fatigue. However, people also experienced more Zoom fatigue when they experienced (1) mirror anxiety from seeing their self-image, (2) hyper-gaze from feeling watched by many faces, (3) feeling physically trapped, and challenges in (4) effort in producing nonverbal cues, and (5) effort in monitoring others’ nonverbal cues, even when controlling for differences in usage dynamics. Relative to men, women also reported greater Zoom fatigue after video-conferencing because they experienced the above nonverbal mechanisms to a greater extent.