Background: The walking school bus (WSB) is a promising intervention to increase walking to school and physical activity in school-age children. The aim of this qualitative study was to assess parent perceptions of a WSB program that was part of a randomized controlled trial to inform future programs. Methods: The authors interviewed 45 parents whose children had participated in a WSB program in the Seattle area, in which third- and fifth-grade students walked to/from school with adult chaperones along a set route. The authors performed a qualitative analysis of the interview transcripts and coded interview segments into 4 broad categories as follows: facilitators, barriers, general positive sentiments, and proposals. Results: Most parents spoke of the benefits of the WSB program; in particular, parents frequently applauded exercise/physical health benefits. Of the barriers, the most frequently cited was time, with work schedule and commute changes leading some families to walk less frequently. Conclusions: Most parents voiced support for the WSB program as a means to improve child health, to learn pedestrian safety, and to interact with positive adult role models. Parents made several suggestions to improve the program, including better recruitment methods, logistical improvements, and a platform for communicating with other parents.