Learning by teaching is an increasingly popular strategy in educational videos, designed to foster active learning. However, the relationship between instructional behaviors and learners’ performance in this context remains underexplored. This study employed a combination of eye-tracking and screen recording techniques to examine how learners’ behaviors while preparing for teaching through video viewing and engaging in subsequent teaching are associated with their own learning performance. The participants were 100 undergraduate students (86 females and 14 males) randomly recruited from a Chinese university, organized into 50 dyads. They engaged in face-to-face interaction, including viewing educational videos to prepare for teaching and subsequent teaching. Correlational analyses indicated that viewing behaviors, such as self-monitoring and rewinding during video viewing, were positively associated with the effectiveness of the learning by teaching strategy. Additionally, instructional behaviors involving elaboration, focused attention on instructional content, and interaction with students were positively correlated with enhanced learning performance. Lag sequential analysis and independent samples t -tests revealed that, compared to low-performers, high-performers were more likely to engage in behavioral sequences such as rewinding and clarifying during video viewing, as well as actively querying, providing feedback, adjusting teaching activities, and elaborating during instruction. Our findings on learners’ behaviors while preparing for teaching through video viewing and engaging in subsequent teaching provided practical insight for the learning by teaching strategy in video lectures to promote active learning. Educational practitioners are encouraged to create opportunities that foster effective learning and teaching interactions identified in this study, and to implement targeted support interventions to enhance the effectiveness of the learning by teaching strategy in educational videos.