In recent years, there has been a growing emphasis on innovative teaching methods in secondary education as educators seek to enhance students' critical thinking abilities and motivation to lean. This research focuses on evaluating the impact of a video-based Problem-Based Learning (PBL) approach on the performance and critical thinking ability of Ugandan Form-2 secondary school students. We assessed students' performance and motivation for critical thinking using a test and their motivation using a motivational scale. The quasi-experimental design involved 144 students selected from four schools in the Sheema District. All students were pretested before the experimental group underwent a video-based PBL intervention and posttested after the intervention. Data entry and analysis were conducted using MS Excel 2016 and SPSS v.25. Inferential statistics revealed a statistically significant difference in critical thinking ability before and after learning the unit on simple machines in physics. Additionally, a positive motivation to learn physics was statistically proven after the intervention. Notably, students from government schools exhibited diverse performance, while private school students showed greater improvement and motivation after the instructional intervention. In conclusion, the results demonstrate that video-based PBL is an effective method for teaching physics and fostering motivation to learn the subject. Consequently, we recommend that teachers incorporate this approach into their daily teaching practices and call upon stakeholders to support the implementation of these resources in the classroom.