The quality of mathematics teaching in Lesotho primary education remains one of the vexing problems in the education system. The study investigated how teachers viewed the impact of instruction on enhancing their knowledge of teaching. Data for the study were elicited from the second-year students enrolled for a Bachelor of Education in the 2009/10 academic year at the National University of Lesotho. Questionnaires and interviews were used for data collection. The findings show that before instruction, the teachers operated with limited knowledge of teaching. At the end of the course the teachers' knowledge of teaching was enhanced. Significant change was apportioned to engaging in reflection and teaching for relational understanding. Implications of the findings for the course, teacher education and professional development are also discussed.