Abstract Background Strong sense of community with one’s neighbors may benefit psychosocial well-being. Moreover, local communities with high level of belonging and social cohesion can have a positive impact on public mental health. This study aims to investigate associations between sense of community and life satisfaction - at both an individual and local community level in a Norwegian county. Methods Data from Trøndelag Health Study 4 (HUNT4: 2017-2019) on 22 939 participants were linked to geographic data of residence from Statistics Norway. The basic statistical unit in Norwegian, known as “grunnkrets,” serves to identify participants’ local communities. These units are subdivisions of municipalities, covering geographically contiguous areas that typically include a few hundred inhabitants. This population-based study enables investigation of variation in sense of community, trust, life satisfaction and psychological distress on individual and community level. Results Seniors (median age 70.3 years) with strong sense of community with their neighbors had more than three times higher odds (95%CI 3.08-3.93) of high level of life satisfaction and less than 0.3 times lower odds (95%CI 0.26-0.33) of psychological distress symptoms vs those with low sense of community, adjusted to sociodemographic variables. The average sense of community varied between local communities (N = 284). At this local geographical unit, strong sense of community was associated with high level of trust, enjoying the neighborhood and high life satisfaction. Conclusions The study can inform public health policy to consider development of social infrastructures that bolster sense of community among seniors within neighborhoods. Policy and action plans targeting to increase the overall sense of community in neighborhoods may contribute to create mental health-promoting and age-friendly local communities in Norway. Key messages • At individual level, sense of community with neighbors are associated with life satisfaction and psychological distress among Norwegian seniors. • The average sense of community varies between geographic local areas and are associated with level of trust, enjoying the neighborhood, average life satisfaction, and psychological distress.