Background: STEM (science, technology, engineering, mathematics) education is attracting increasing public interest and policy attention and being promoted at different educational levels in Cambodia. Purpose: The study seeks to identify factors associated with Cambodian university freshmen's choice of STEM major and how significant associations differ by gender and university location. Sample: The study draws on primary data collected from a survey of 2,016 freshmen at 15 universities across Cambodia. Design and method: Binary logistic regression was applied to detect correlates of major choice (dichotomized into STEM major and non-STEM major). Results: Students who choose a STEM major are likely to be male, have clearly prioritized the major since high school, have high self-efficacy in the chosen major, want a career in STEM, enrol at a Phnom Penh-based university, excel at mathematics at high school, excel at science at high school, have no job while studying, and value the importance of science and technology to society. When moderated by gender and university location, only excellence in mathematics, excellence in science, and STEM career prospects remained significantly associated with STEM major choice. Conclusion: Student experience in learning mathematics and science subjects at high school and their exposure to career information and guidance are vital in widening participation in STEM disciplines at higher education level in Cambodia.