Access to natural outdoor environments in cities may promote physical activity and improve human’s health and wellbeing. This study aimed to quantify the impacts on the health and health-related economics of an urban riverside regeneration, which consisted on creating the Besòs riverside Park by providing access to the riverbanks and creating a huge green area next to the river.A counting campaign and a survey of riverside Park users describing their physical activity levels, the duration, and frequency of their visits to the regenerated area, were used to estimate their metabolic equivalent of task (MET-min/week). We used a bespoke quantitative risk assessment tool, which related physical activity (in MET-min/week) and health outcomes obtained from existing meta-analyses, to estimate the age and sex-specific health impacts in terms of all-cause mortality, morbidity (including ischemic heart disease; ischemic stroke; type 2 diabetes; cancers of the colon and breast; and dementia) and disability-adjusted life years (DALYs). We conducted a health economic evaluation in terms of the value of statistical life and direct health costs.Almost 6,000 adult users visited the regenerated riverside Park daily and performed different types of physical activities (i.e. walking for leisure or to/from work, cycling, and running). Among these users we estimated an annual reduction of -3.4 (95% CI; -10.8; -0.1) deaths, -6.2 (95% CI; -19.4; -0.5) cases of diseases, and -11 (95% CI; -36.8; -0.5) DALYs. We estimated savings of -11.4 (95% CI; -36.9; -269,642) million Euros on mortality and direct health-care costs.The urban riverside regeneration of the Besòs riverside Park has resulted in substantial quantifiable benefits to the public health in terms of increased physical activity. Similar accessible riverside renewal projects might improve the health of urban populations, mitigating major public health challenges resulting at least partly from physical inactivity.