BackgroundPhysical activity promotes health, and physical activity done outdoors in nature may be particularly beneficial. We conducted two randomized studies to examine the implementation of a winter hiking intervention and whether this intervention affected activity choices and aspects of well-being during the COVID-19 pandemic.MethodsConvenience samples of adults (n = 53; n = 51) were recruited into two different randomized studies in 2021 and 2022 respectively. Participants completed online surveys at baseline and 6 and 11–12 weeks later. Participants were randomized to a study group (intervention or control) shortly after the baseline assessments. In both studies, the intervention group received free access to a regional winter hiking challenge. In the second study, we also provided winter traction cleats to this group to facilitate engagement in the hiking challenge. Descriptive statistics were used to summarize intervention implementation, including participants’ engagement in challenge hikes. Repeated measures ANOVA models were used to test intervention effects on key outcome variables, including hiking frequency via the Pleasant Activities List, stress via the Perceived Stress Scale, and sleep duration via the Pittsburgh Sleep Quality Index.ResultsIn the first study, the intervention group’s engagement in challenge hikes was low (38.5%); reported barriers included access to winter hiking equipment. In the second study, when winter traction cleats were provided, engagement in the intervention was higher, and the intervention increased hiking frequency and improved sleep. There were no significant intervention effects on stress, but the direction of effects was in the expected direction.ConclusionsResults highlight some potential positive impacts of this intervention designed to facilitate access to winter hiking. Future research could examine whether effects are stronger in a larger sample, in which additional barriers to engagement are addressed.Trial registrationThis study was registered at clinicaltrials.gov on 28/12/2020 prior to participant enrollment (NCT04685681),https://clinicaltrials.gov/ct2/show/NCT04685681.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12889-023-15696-7.