Background The transition to university often involves a change in living arrangement for many first-year students. While weight gain during first year of university has been well documented, Canadian literature on the impact of living arrangement within this context is limited. The objective of this investigation was to explore the effect of living arrangement on anthropometric traits in first-year university students from Ontario, Canada. Methods 244 first-year undergraduate students were followed longitudinally with data collected early in the academic year and towards the end of the year. Anthropometric parameters including weight, waist and hip circumference, body mass index (BMI), and waist-to-hip ratio (WHR) were examined. The Wilcoxon signed-rank test was used for pairwise comparison of traits from the beginning to end the year in the absence of adjustments. Additionally, linear regression models with covariate adjustments were used to investigate effect of the type of living arrangement (i.e. on-campus, off-campus, or family home) on the aforementioned traits. Results In the overall sample, a significant weight increase of 1.55kg (95% CI: 1.24–1.86) was observed over the school year (p<0.001), which was also accompanied by significant gains in BMI, and waist and hip circumferences (p<0.001). At baseline, no significant differences were found between people living on-campus, off-campus, and at home with family. Stratified analysis of change by type of living arrangement indicated significant gains across all traits among students living on-campus (p<0.05), and significant gains in weight and BMI among students living at home with family. Additionally, a comparison between living arrangements revealed that students living on campus experienced significantly larger gains in weight and BMI compared to students living off-campus (p<0.05). Conclusion Our findings indicate that living arrangement is associated with different weight gain trajectories in first-year university students.