Evidence regarding the benefits of an instructor's deictic gestures in video lectures on adults' learning may not necessarily be reflective of their effect on children's learning. Furthermore, there is a lack evidence regarding how deictic gestures specifically affect learners' learning process. Based in cognitive load theory, with consideration of the signaling principle and embodiment principle in multimedia learning, the present study sought to determine whether an instructor's deictic gestures affected young adults' and children's learning from video lectures differently. Participants consisted of 60 college students as the young adults sample and 63 pupils as the children sample. Each participant viewed one of two video lectures, either with or without the instructor using deictic gestures. During the experiment, participants' eye movements, prior knowledge, learning process, and learning performance were recorded and measured. The results of nonparametric tests showed that when the instructor used deictic gestures, the children paid more attention to the video content while the young adults reported a higher learning experience. Both groups demonstrated improved learning performance, regardless of age. Our findings highlight the fact that young adults and children do learn differently from video lectures with an instructor using deictic gestures. Furthermore, our findings contribute to understandings regarding the design of video lectures and video-based learning, specifically, that if an instructor is presenting the content in video lectures, they should be encouraged to use deictic gestures to improve students' learning.