Walking, a physical activity beneficial for both physical and mental health, is influenced by various factors. Although previous studies have acknowledged that walking behavior is influenced by environmental and psychosocial factors, little is known about their interactions. Based on a socio-ecological model and focusing on Chinese college students, the purpose of this study was to examine the influence of campus walkability and psychosocial factors on college students’ walking behavior, including the interactions between these factors. This study seeks to enhance understanding of how to promote walking behavior through campus environmental design and psychological interventions. Multiple regression analysis was conducted on the questionnaire data. Findings revealed that campus walkability significantly influenced both walking behaviors, alongside psychosocial factors such as attitude, self-efficacy, perceived benefits, perceived barriers, and subject norms. Additionally, significant differences in interaction effects between these factors were observed for purposeful versus recreational walking behaviors. These interactions suggest that campus walkability more substantially promotes walking behavior in students with negative psychosocial factors, whereas its impact is less pronounced in those with positive psychosocial factors. The results underscore the need to focus not only on developing walkable environments but also on understanding the synergies with the psychosocial factors of target populations, offering crucial insights for campus planning and health promotion practices.