BACKGROUND: In communities affected by a disaster, walking can be a feasible form of physical exercise to improve physical and mental health conditions. However, there is limited evidence to support relationships between walking habits and mental health conditions in post-disaster settings. Cross-sectional epidemiological data obtained from a questionnaire survey (conducted in October 2017) of a community affected by the 2011 Great East Japan Earthquake (GEJE) was analyzed to evaluate the relationships. METHODS: Participants included individuals over 20 years of age (N = 718) from Shichigahama town in Miyagi prefecture, whose houses were significantly damaged by the GEJE. Their mental health conditions were assessed by the Kessler Psychological Distress Scale (K6), the Center for Epidemiologic Studies Depression Scale (CES-D), and the Impact of Event Scale-Revised (IES-R). Additionally, the questionnaire asked the participants spent duration walking on average and their walking purpose by the following items: (1) longer than 60 min per day, (2) between 30 and 60 min per day, or (3) less than 30 min per day, and whether they walked to maintain healthy living habits (health-conscious walkers) or merely for transportation without considering health consequences (non-health-conscious walkers). These information and mental health indicators were analyzed using analysis of covariance (ANCOVA). RESULTS: Among the three walking duration groups of health-conscious walkers, there were significant differences in CES-D and K6 scores (p = 0.01 and p = 0.04), but not in IES-R scores, considering age, gender, and alcohol drinking habits as covariates. CES-D score was significantly higher among short walkers (p = 0.004). Among the three walking duration groups of non-health-conscious walkers, there were significant differences in avoidance symptoms, the subdomain of IES-R (p = 0.01), but not in CES-D, K6, and total IES-R scores, considering the variants. CONCLUSION: Our study suggests that walking durations may positively affect mood, but not PTSR, only when walking is performed with the purpose of maintaining healthy living habits. Walking durations were negatively associated with avoidance symptoms among non-health-conscious walkers in the community affected by the GEJE, indicating that the disaster may have had a long-lasting impact on walking habits.