This study investigated the effect of the use of Activity-Based Learning (ABL) method on junior secondary school students’ achievement in mathematics when they were taught trigonometric ratios using geotrigmetric sets. The population size was 3,835 while the sample size was 100 in a quasi experimental research design. The instrument used for data collection was a researcher-made mathematics achievement test with r = 0.87. Analysis of covariance (ANCOVA) was used for data analysis. Results showed among others that the activities which were generated by the use of geotrigmetric sets brought about a significant effect on achievement of the experimental group of students compared to students in the control group. Based on the results of the study, it was recommended that teachers should adopt the use of the geotrigmetric sets to generate enough and sufficient activities for students while introducing them to trigonometric ratios at the junior secondary school level.