© 2019, Springer Nature Switzerland AG. Background: Mental health problems are highly prevalent among college students in many countries. However, evidence suggests that many at-risk students do not receive professional help. Objective: We aimed to understand which students are most likely to have unmet need for mental health services. Given increasing and widening participation in higher education, we focused attention on disparities by socioeconomic background. Methods: We analysed data from a recent survey of over 6000 students enrolled in higher education in Ireland. Using three separate measures of mental health problems, namely stress, anxiety, and depression, we developed and modelled an indicator of unmet need. Results: We found that students from the lowest social class and students with the greatest difficulty in making ends meet have higher rates of unmet need overall, but that these disparities disappear once we control for mental ill-health. For those with mental health problems, unmet need is shown to be independently higher for students who are younger, male, heterosexual, and studying for a Ph.D. We also found a strong independent association between unmet need and self-stigma, as well as considerable differences in unmet need across institutions. Conclusion: Socioeconomic disparities in unmet need are driven by higher rates of mental ill-health among those from lower socioeconomic backgrounds. Our findings have implications for the targeting of services, as well as the provision of information about mental health and associated services.