The purpose of the study was to establish lecturers and student teachers' perceptions of the importance of subject matter knowledge and how these views affected supervision and assessment of pre-service and in-service science teachers at University of Mashonaland (pseudonym) in Zimbabwe. The study was largely qualitative and used group discussions, interviews and document analysis to collect data. Lecturers that offered professional courses had varied backgrounds with the majority claiming a background in science education at university level and a large number did not study science beyond Ordinary Level. There were mixed feelings about quality of supervision and assessment received from lecturers who did not have sound science knowledge. Student teachers thought they did not benefit much from supervision by non-science educators and their view was supported by science educators. On the other hand lecturers with no science background insisted they were competent to assess documents and live lessons conducted by the student teachers. Further research was recommended to determine qualitative and quantitative differences in supervision and assessment by lecturers with different backgrounds in science education.