This case study investigated the conceptual understanding of the Simple Pendulum topic amongst physics student-teachers using online experiments. A pre-experimental design was utilised, employing a one-group pretest-posttest approach with 20 student-teachers. The research instruments included a highspeed video activity conducted within Online Experiments (OEs) and a conceptual understanding test assessing various aspects of the Simple Pendulum topic. Average gain and normalised gain were employed to assess student learning progress. The findings revealed that OEs had a significant positive impact on students' understanding of oscillation concepts, particularly the Simple Pendulum. Following the intervention, most students exhibited improvement in their learning outcomes. The average score increased significantly, from 35.25% in the pretest to 82.50% in the posttest. Normalised gain scores, ranging from 0.20 to 1.00, confirmed substantial improvement in students' understanding of scientific concepts.