YouTube educational resources can help improve physics classroom instructional practices to promote learning. This study investigated the impact of integrating YouTube-based virtual labs on learners' engagement and understanding in physics classrooms. The study was conducted in a secondary school in Nairobi City, Kenya. The participants were secondary school physics students in classes from one to two. The study applied a mixed research approach. The study participants were grouped into two groups: an experimental group and a control group. Unlike the control group, the experimental group was subjected to YouTube-based virtual labs. The study relied on quantitative data from achievement tests and qualitative data from observations during Virtual labs integrated physics classroom and focus group discussions. The results from achievement tests revealed no significant difference in performance between the experimental and control groups. On the contrary, focus group discussion results showed that incorporating YouTube-based virtual labs in physics classrooms improves learners' understanding. Finally, research findings from focus groups and observations signified that integrating YouTube-based virtual labs in physics classrooms improves learners' engagement.