Pupils’ lack of interest in mathematics at tender ages in primary school has been observed to be one of the major causes of low performance in the subject as learners progress in the academic pursuit. Among other factors, Teacher-Pupil relationship remains one of the grey areas that require an in-depth examination to understand its influence on the pupils’ interest in mathematics in Osun State primary schools. This study, therefore, investigated the influence of teacher-pupil relationship on pupils' interest in learning Mathematics, so as to enhance teachers’ knowledge on strategies to adopt for improving pupils’ academic achievement in mathematics. The study adopted a descriptive survey research design. A total of 100 pupils were randomly selected from both public and private primary schools in Ife Central Local Government Area. Data was collected using a validated questionnaire with a reliability coefficient of 0.82 determined through Cronbach’s Alpha coefficient and analyzed using frequency count and regression analysis. The results showed that teacher–pupil relationship in Mathematics classroom is positive, that the interest of pupils in learning Mathematics is high and that there is a significant relationship between teacher-pupil relationship and pupils’ interest in learning Mathematics in the study area. The study then concluded that positive teacher–pupil relationship is crucial to pupils’ interest in learning Mathematics and recommended that teachers should continuously strengthen teacher-pupils relationship skills through trainings, pupil-centered pedagogies, regular mentorship and feedback systems.