The present study investigated the effectiveness of interteaching versus traditional lecture-based teaching in two 9-week online asynchronous classes. Participants were undergraduate students enrolled in one of two sections of a psychology of learning course (N ϭ 62). The study used an alternating-treatments design, switching between interteaching and lecture-based teaching throughout the term. Type of instruction was counterbalanced across sections, so that material taught using interteaching in one section was taught using a standard lecture format in the other section. Results showed that weekly exam scores were significantly higher following interteaching compared to standard lecture-based teaching, p Ͻ .001, p 2 ϭ 0.18, 95% CI [0.03, 0.35]. Students also scored more points on the final exam on material that had been taught using interteaching, p Ͻ .001, p 2 ϭ 0.20, 95% CI [0.04, 0.36], which indicates that interteaching improves long-term retention of information. Students reported learning more during interteaching and rated the overall quality of interteaching as significantly higher than standard lecture, p ϭ .002, p 2 ϭ 0.18, 95% CI [0.03, 0.35]. Overall, the present findings showed that interteaching was more effective and preferred than standard lecture in an online asynchronous classroom, which suggests that the benefits of interteaching are not limited to traditional classroom environments.