Objectives: (1) To investigate weight gain in first-year university students; and (2) to examine whether environmental and psychological factors, specifically accommodation and stress, predict weight gain. Methods: Eighty-four first-year university students (77 per cent female) were weighed and completed the Perceived Stress Scale (Cohen, Kamarck and Mermelstein, 1983) and a health habits questionnaire at the beginning and end of their first semester of university (Mean duration = 76.67 days, SD = 1.76). Results: Weight gain was small, but significant (M = 0.89 kg, SD = 3.30). Students living on-campus gained more weight than their off-campus peers, M = 1.65 kg and 0.13 kg respectively, t(82) = -2.32, p less than 0.05. No significant relationship was found between stress and weight change. Conclusions: These results suggest that the first year of university is a critical period for weight gain, especially for students living in residence. Greater understanding of risk factors associated with weight gain in first-year university students, particularly students living in residence, could lead to prevention of this weight gain and potential subsequent overweight and obesity. (Contains 2 tables.)