This study examined secondary school students and science teachers’ conceptions of the nature of scientific knowledge (NOSK). A pragmatic research philosophy was adopted in this study. To address the objectives of the research, a mixed methods approach was employed. Open-ended questionnaires were used to collect data from 134 students, and 48 science teachers. The participants were selected from three schools using a convenient sampling technique. Qualitative analysis involved comparing students’ and teachers’ responses to experts’ views of NOSK. Frequency counts and percentages were also used to describe the NOSK conceptions of the participants. In addition, the Mann-Whitney U test was used to compare students’ conceptions of NOSK by grade level and gender. The findings showed that most of the secondary school students had naïve conceptions about NOSK. On a comparative basis, grade 12 students reflected more informed NOSK views than grade 10 students on most of the tenets. Mann Whitney U test revealed that the mean rank score of grade 12 students is significantly greater than grade 10 students on the subjective (U=3.20, p<.05) and cultural (U=2.42, p<.01) aspects of NOSK. The teachers generally held a naïve conception of NOSK, as evidenced by the fact that their conception aligned with informed conception only on two of the seven assessed NOSK aspects. The findings indicated that there is a need to devise mechanisms to develop secondary school students’ and teachers’ NOSK understanding to attain its promised benefits. Future research should investigate students' and teachers' NOSK conceptions using large samples across grade levels, from diversified schools, including private and public schools from the different regions of the country to reveal students’ and teachers’ NOSK conceptions.