The achievement of a sustainable urban environment and health for all requires the engagement and greater awareness of local communities on issues of environment and health. This HORIZON2020 CitieS-Health study presents the outcomes of the environmental epidemiological research on the participants’ acquisition of new skills and knowledge as well as on health behaviour. We conducted a cross-sectional study of 1062 residents of Kaunas city, Lithuania, from 2019 to 2021. We analysed the associations between the neighbourhood environmental quality scores and health issues, and the self-reported ratings on the acquired knowledge measured using a Likert rating scale. About 42.7% of the participants acknowledged that participation in the research study improved their data collection and interpretation skills, and 58.8% of them stated that the participation improved their knowledge on the links between environmental quality and health. The participants with increased knowledge more often rated their health as “good”, had a significantly lower diastolic blood pressure, and regularly visited the natural environment. The high impact of participatory research was associated with a higher scoring of the neighbourhood environmental quality, higher physical activity, and a beneficial effect on health. The study provides scientific evidence that improving the neighbourhood environment would promote increased physical activity, such as reaching green spaces by walking, and might benefit the society.