A study in Plateau State, North-Central Nigeria on the effects of the Experiential Spatial Problem-based Learning (ESPBL) Model on the achievement and retention of knowledge in Geography problem-based topics. Driven by four research questions and hypotheses, the study employed a quasi-experimental design for non-equivalent samples and a randomly selected sample of 47 Geography students spread into an experimental group (27 students) and a control group (20 students). Data was collected using the Spatial Problem-based Achievement Test (SPBAT) with a reliability coefficient of .96 tested using the Pearson Product Moment technique. The study's data was analysed using mean and standard deviation to answer the research questions and analysis of covariance (ANCOVA) and Linear Regression Model (LRM) to test the formulated hypotheses. Findings revealed that the ESPBL model significantly increased the achievement and knowledge retention of students in the experimental group compared to the control group. The Treatment was responsible for the students' ability to maintain statistically equal scores in the posttest achievement and the retention test. The study also realized that students' retention of knowledge was predicted by achievement. Thus, students who achieved high scores on the achievement posttest also achieved high scores on the retention test. It was concluded that the ESPBL model is effective in improving students' achievement and retention in Geography problem-based topics. The study recommended that the strategy should be employed at all levels for implementing the Geography curriculum and other science and social science disciplines, especially where the objective of teaching is to solve a known problem.