Aim: To investigate whether commercial coaching affects performance in the Undergraduate Medical and Health Sciences Admission Test (UMAT). Method: The effect of coaching on the UMAT scores of 402 final high school students applying for medicine was examined using t-tests and multiple regression analyses that controlled for academic performance, high school type and gender. Results: Over half (56.2%) of the participants had enrolled in commercial coaching. Coaching had no influence on UMAT Section 1 or 2, even after controlling for academic performance, gender and type of high school. UMAT Section 3 was significantly higher for coached students, but this was only the case for high ability students. Coaching had a slight negative effect for lower ability students. Those attending academically selective high school also had higher UMAT scores. Conclusion: The results have implications for the fairness and validity of the UMAT. The differential effect of coaching possibly occurred because high academic ability students are able to learn solution rules for non-verbal tests. We propose that the effect of school type relates to a competitive culture that drives extended test practice in academically selective schools.