Evidence on the effects of a community-wide intervention (CWI) on population-level physical activity (PA), especially in the long term, is limited. Therefore, we evaluated the five-year effect of CWI on promoting PA through information dissemination, education, and community support primarily targeting older adults, by incorporating Japanese guidelines, in Fujisawa City, from 2013. To assess the effect of the whole-city intervention, we distributed questionnaires in 2013, 2015, and 2018 to three independent random samples of 3,000 community-dwelling adults (aged ≥ 20 years) using a quasi-experimental study design. Three separate samples responded to the survey (41% at baseline, 46% at the two-year mark, and 48% at the five-year follow-up). The primary outcome was change in PA participation. At the five-year follow-up, PA (median: 120 minutes/day) was significantly higher than at baseline (86 minutes/day) and the two-year follow-up (90 minutes/day). The results of the multivariate analysis indicated that PA among older adults-the primary target population of the CWI-increased significantly at the five-year follow-up, compared to those aged 20-64 (mean difference of change between groups: 14.7 minutes/day, P= 0.029). Among older adults, PA was significantly lower in those with poorer perceived economic status than in their more well-off counterparts at the two-year follow-up (P= 0.003); however, there was no significant difference at the five-year follow-up (P= 1.000). There was a positive interaction between group and period (mean difference of change between groups: 40.9 minutes/day, P= 0.001). In conclusion, the five-year CWI targeting older adults, incorporating national guidelines, improved population-level PA.