The investigation explored the comparative effects of individualised and cooperative learning strategies on secondary school students' interest in Mathematics, focusing on topics such as Venn diagrams, union sets, intersection sets, empty sets, and measures of central tendency. It formulated two hypotheses and research questions directed the investigation. The study was carried out in Anambra State's Awka Education Zone using a quasi-experimental approach with targeted population of 8,583 SS II Mathematics students from 65 co-educational secondary schools. Six schools were randomly selected, resulting in a sample of 270 students (100 males and 170 females). Data was collected using the Mathematics Interest Inventory (MII), structured from Surya and Arty's Chemistry Attitude and Interest Questionnaire Scale (2020). The MII underwent face and content validation, achieving a reliability coefficient of 0.73 through Cronbach's alpha. Analysis of Covariance (ANCOVA) assessed the hypotheses at a 0.05 significant level, whereas mean and standard deviation analyses addressed the study issues. The findings indicated that cooperative strategies enhance interest, though no significant difference was observed. Individualised learning produced higher interest among males, while females showed more engagement with cooperative methods. The study recommended government support for teacher training in individualised strategies and the promotion of cooperative learning in the curriculum to improve interest in Mathematics, leading to conclusions and educational implications for teaching practices.