Non-local ethnicity or nationality and lower English proficiency have been linked with poor performance in health professional education. This study sought to compare the relative contributions of ethnicity and English proficiency, and to do so in a context where students had not been selected via interviews or some other proxy for language proficiency. Ethnicity, citizenship, and demographic data, as well as academic performance and progress were obtained for three successive cohorts (entering in 2007, 2008 and 2009) into a three-year pharmacy programme, following a common first-year. Complete data was available for all 297 students entering via this path. By the end of the programme, controlling for grades at entry, students from some non-local ethnic backgrounds (p < 0.001) underperformed local students, as did males (p < 0.001) and those who had been identified as having low English proficiency in year 1 (p < 0.01). Males (p < 0.01) and one non-local ethnic group (p < 0.01) were also more likely to have to repeat a year of study. Ethnicity was a stronger predictor than English proficiency or acculturation, but English proficiency was still independently and additively predictive. This suggests that targeted support strategies for students with lower English language proficiency are still important, but that cultural differences should not be underestimated.