Background: Among Belgian adolescents active transport (AT) is a common physical activity (PA) behavior. Preliminary evidence suggests that AT can be an important opportunity for increasing adolescents' daily PA levels. To inform interventions, predictors of this PA behavior need to be further explored. Therefore, in the perspective of the ecological models this study aimed (a) to investigate the relationship between the perception of neighborhood built environmental attributes and adolescents' AT and (b) to explore the contribution of the perception of neighborhood built environmental attributes beyond psychosocial factors. Methods: For the purpose of this study, data from the Belgian Environmental Physical Activity Study in Youth (BEPAS-Y), performed between 2008 and 2009, was used. The final study population consisted of 637 adolescents aged 13-15 years. The participants completed a survey measuring demographic and psychosocial factors, the Flemish Physical Activity Questionnaire and the Dutch version of the Neighborhood Environmental Walkability Scale. Results: A set of stepwise linear regression analyses with backward elimination revealed that a shorter distance to school, perceiving neighborhoods to have connected streets, a lower degree of land use mix diversity, less infrastructure for walking and a lower quality of the infrastructure for walking are associated with more min/day AT to and from school (p all < 0.05). Furthermore, marginally significant associations (p < 0.10) were found between residential density and safety from crime and AT to and from school. No relationship between the perception of the neighborhood built environmental attributes and walking for transport during leisure time and cycling for transport during leisure time was found. Conclusions: The substantial contribution of the perception of neighbourhood built environmental attributes to AT found in Belgian adults, could not totally be confirmed by this study for Belgian adolescents. Among Belgian adolescents, the contribution ...