The convenience sample used in the study reported on here consisted of 91 students enrolled in the primary and middle school Postgraduate Certificate in Education course for 2 consecutive years at a South African university. We used the Student Understanding of Science and Science Inquiry instrument to answer questions about these students' knowledge of the nature of science and scientific inquiry compared to that published for pre-service primary and middle school teachers from China, Turkey, and the United States of America (USA), whether the changes proposed for the instrument enhanced its reliability, and whether any correlation could be found to these students' age and educational factors. The findings show that these South African student teachers shared similar levels of knowledge of the nature of science and scientific inquiry to their counterparts from Turkey and the USA, all of which were less sophisticated than that of the Chinese students. The test was found to have a high degree of reliability in the South African context, with the proposed changes to the instrument doing little to enhance this. The older students and those who did not study any tertiary science or mathematics courses scored statistically significantly higher. We suggest that the confirmatory nature of tertiary practical science work and exposure to the complexity of science in postgraduate work or employment in industry could explain these findings.