The study aimed to investigate the extent to which students' epistemological beliefs in the dimension of control of knowledge acquisition relate to performance in the subject of physics. The study used a mixed-methods research approach that included philosophical analysis, a descriptive survey and a correlational analysis. The research was steered by both the implicit intelligence philosophy and the constructivist learning theory. The sample size comprised 310 form two students, 60 physics teachers and 20 heads of the science department. Quantitative data analysis techniques, including correlation and regression analysis, were used to examine the relationships between students’ epistemological beliefs in control of knowledge and physics performance. The qualitative data from interviews provided deeper insights into how students’ experiences and perceptions related to their beliefs about knowledge and physics performance. Data analysis was performed using tools in the SPSS version 26. The study revealed a positive correlation between sophisticated beliefs in control of knowledge acquisition and performance in physics. From the findings of the study, the researcher concluded that sophisticated beliefs in control of knowledge acquisition contribute towards better performance in physics. The study suggests the implementation of strategies aimed at fostering the development and adoption of sophisticated epistemological beliefs in control of knowledge acquisition among students to enhance their performance in physics. The outcome of this study can inform educational policymakers, curriculum developers, and teachers in Kenya to design interventions that promote the development of students’ epistemological beliefs in control of knowledge to stimulate performance in physics.