OBJECTIVE: Many students who need mental health support do not receive it. We examined associations between perceived barriers and university mental health service access. Participants: First-year Oxford University undergraduates (n = 443) with unmet mental health needs. METHODS: Logistic regression tested which perceived practical, attitudinal, and stigma-related barriers predicted service use. Subgroup analyses targeted screen-positives for anxiety (GAD-7) and/or depression (PHQ-9). RESULTS: Reduced service use was linked to attitudinal barriers, minimizing problems (OR = 0.64; CI = 0.42-0.98) and difficulty discussing problems (OR = 0.59; CI = 0.38-0.91), especially among screen positives for the latter (OR = 0.49; CI = 0.27-0.89); practical barriers, uncertainty about how to get help (OR = 0.64; CI = 0.42-0.97) and time limitations (OR = 0.66; CI = 0.44-0.98), especially in screen-positives for both (OR = 0.46; CI = 0.26-0.79; OR = 0.47; CI = 0.27-0.79); and stigma-related barriers, feeling ashamed (OR = 0.63; CI = 0.40-0.98), appearing weak (OR = 0.65; CI = 0.42-0.98), and friends' reactions (OR = 0.58; CI = 0.38-0.88). CONCLUSIONS: Multiple perceived barriers were associated with a reduced likelihood of accessing university mental health services. Developing mental health literacy and streamlined pathways may improve timely support access for students with unmet needs.