One of the critical goals of teaching chemistry is to enable learners to gain conceptual understanding. Traditional instruction has often been associated with rote memorisation, resulting in learners failing to explain observed chemical phenomena, make predictions based on acquired concepts, advance convincing arguments, and engage in meaningful problem-solving and critical thinking. Therefore, the study aimed to describe the conceptual understanding of the learners taught Reaction Kinetics using computer simulations supported by the Predict-Observe-Explain strategy. The study was guided by Holme, Luxford, and Brandriet's five categories of conceptual understanding--transfer, translation, problem-solving, prediction, and depth as the conceptual framework. This was a descriptive study in which a case study research approach was used. Five purposively sampled grade 12 learners participated in the study, representing the range of cognitive abilities from a secondary school class of 53 learners. Semi-structured interviews were used to collect data. The responses of the five participants were analysed using the qualitative content analysis. The findings were that most of the learners' responses were in the sound understanding sub-category, some were in the partial understanding sub-category, and a few were in the no understanding sub-category, which made us conclude that computer simulations supported by the Predict-Observe-Explain strategy assisted the learners in conceptual understanding. The learners gained an understanding of most concepts, although their responses in the partial understanding sub-category showed difficulties related to depth, transfer, and translation. These findings are expected to assist chemistry teachers, teacher educators, and curriculum planners in improving learners' conceptual understanding of chemistry.