Background: The Dementia Supporter Initiative is a national public education program in Japan that aims to foster positive attitudes and appropriate understanding of dementia to support people with Alzheimer's disease and related dementia in the community. However, its influence on the community as a whole remains unclear. Objective: This study examined the relationship between dementia supporter training and residents' attitudes and recognition related to dementia at the municipal level. Methods: This ecological cross-sectional study linked municipal-level data from the Japan Gerontological Evaluation Study 2022 wave with publicly available information on the number of dementia supporters. Residents' beliefs and attitudes toward dementia and recognition of dementia consultation services were assessed by mail questionnaires and aggregated at municipal level. The proportion of dementia supporters in each municipality was calculated as of September 2022. Results: Data from 69 municipalities were analyzed. The mean proportion of dementia supporters was 13.47% (2.62-44.85). A higher proportion of dementia supporters was positively correlated with community support-seeking for a family member with dementia (r = 0.328) and recognition of dementia consultation services (r = 0.501). Regression analysis adjusted for municipal covariates also showed their positive associations (per 10-percentage-point increase: coef. = 1.44, p = 0.047; coef. = 3.12, p < 0.001, respectively). No associations were observed with residents' positive attitudes and appropriate understandings of dementia. Conclusions: Wider dissemination of dementia supporters may contribute to better recognition of community support resources, but may be insufficient to influence broader public attitudes and understanding of dementia at the community level.