Background: The adoption of the flipped classroom in undergraduate medical education (UME) calls on students to learn from various self-paced tools -including online lectures -before attending in-class sessions. Hence, the design of online lectures merits special attention, given that applying multimedia design principles has been shown to enhance learning outcomes. Objective: To understand how online lectures have been integrated into medical school curricula, and whether published literature employs well-accepted principles of multimedia design. Methods: This scoping review followed the methodology outlined by Arksey and O'Malley (2005). MEDLINE, PsycINFO, Education Source, Francis, and ProQuest were searched to find articles from 2006 to 2016 related to online lecture use in UME. Results: 45 articles met inclusion criteria. Online lectures are used in preclinical and clinical years, covering basic sciences, clinical medicine, and clinical skills. The use of multimedia design principles is seldom reported. Almost all studies describe high student satisfaction and improvement on knowledge tests following online lecture use. Conclusions: Integration of online lectures into UME is well-received by students and appears to improve learning outcomes. Future studies should apply established multimedia design principles to the development of online lectures to maximize their educational potential.