Abstract: It is believed that involving the public in street tree (i.e. curbside or sidewalk tree) stewardship is an essential part of achieving urban forest canopy goals. However, the incremental benefits of such involvement have not been well studied. Because urban forest stewards contend with many factors that can reduce street tree longevity and offset the benefits of stewardship, quantifying and communicating the overall benefits may help spur stewards’ commitment. To assess the net effect of volunteer street tree stewardship, this article summarizes the development of a community-wide street tree stewardship program and the impact of stewardship on street tree mortality rates over a span of five years. Binary yes-or-no data on whether a steward cared for a street tree were collected for 3,083 growth years, 1,036 of which were for street trees assigned to street tree stewards. The street trees tracked encompassed every street tree within the highly urbanized TriBeCa* neighborhood in lower Manhattan. It was found that significant differences in street tree mortality rates were observed when street trees were stewarded. Odds ratios show an expectation of substantially reduced street tree mortality rates when tree stewards are caring for trees. Other factors regarding where the data was collected, especially specific neighborhood characteristics that may have had an effect on the study, are discussed.