Insufficient level of physical activity (PA), and higher sedentary behaviour are a serious health concern among university students. Active commuting, such as walking or cycling, provides an opportunity to increase PA levels, and decrease time spent in sedentary behaviour. PURPOSE: This study aims to describe, compare and identify associations between self-reported commuting behaviours and commuting-related device-measured PA and sedentary behaviour for each mode of commuting to and from university (i.e., active, public and private). METHODS: A total of 63 university students (65.1% women) participated (20.6 ± 3.8 years old) from a public university in Cadiz, Spain. Mode of commuting, PA and sedentary behaviour were self-reported, and device measured. Differences in commuting self-reported measures and the commuting-related device-measured PA and sedentary behaviour were analysed using the Kruskal–Wallis test. Additionally, to ascertain differences between groups, the Mann-Whitney test was used. Associations between commuting-related device-measured PA and sedentary behaviour to and from university with self-reported were studied using linear regression. RESULTS: Commuting time, commuting distance, and commuting speed to and from university were lower in active than public and private commuters (all, p < 0.001). The commuting energy expenditure per minute was higher in active commuters followed by public and private commuters (all, p < 0.001). Active commuters displayed significant differences (p < 0.05) with public and private commuting in all PA levels and the sedentary behaviour to and from university. Active commuters presented positive associations in commuting time, commuting distance and total commuting energy expenditure with MVPA to university (B; 95% CI = 0.08; 0.04, 1.25; 0.01; 0.00, 0.02; and 3.70; 1.98, 5.42 respectively) and from university (B; 95% CI = 0.87; 0.41, 1.33; 0.07; 0.03, 0.10; and 3.16; 1.47, 4.85 respectively). CONCLUSION: Active commuting involved the highest levels of energy expenditure per minute and contributes to 44% weekly of the moderate-to-vigorous PA (MVPA) recommendations to obtain health benefits. Based on self-reported questions, this study presents new evidence to obtain a quantitative measure (METs) to delve into variables of commuting behaviours.