Abstract Background Gender is increasingly recognised as a critical factor in designing community-based health promotion programmes. Men’s Sheds (‘Sheds’) are community-based informal environments that represent a safe space in which to engage cohorts of hard-to-reach (HTR) men in health promotion. Sheds for Life (SFL), the first structured health promotion initiative evaluated globally in Sheds, is a 10-week initiative co-designed with Shed Members (Shedders) and delivered directly in the Shed setting in Ireland. This research describes the health and wellbeing outcomes experienced by SFL participants. Methods Purposive sampling was used to recruit a diverse representation of Shedders (n = 421) participating in SFL alongside a wait list control (n = 86). Questionnaires assessing constructs of health and wellbeing were administered one-to-one in Sheds at baseline, 3, 6 and 12 months. Descriptive data for health outcomes were generated for each time point and assessed for significant changes using inferential testing, while considering COVID-19 impact. Results Outcomes related to subjective wellbeing, mental wellbeing, physical activity, social capital and healthy eating significantly increased post SFL (p < 0.05). Mental wellbeing scores (SWEMWBS) post SFL remained significantly higher than baseline despite COVID-19 impact (p < 0.05). Binary logistic regression indicated that the odds of a meaningful SWEMWBS change was significantly higher for shedders that had lower SWEMWBS (OR 0.804), less loneliness (OR 0.638) and lived alone (OR 0.456) at baseline. Shedders with lower SWEMBWS had higher odds of experiencing positive changes in life satisfaction (OR 0.911) and trust (OR 0.928), while Shedders who lived alone had also higher odds of experience positive changes in healthy eating (OR 0.481). Finally, inactive Shedders at baseline had higher odds of experiencing increased levels of physical activity (OR 0.582). Conclusions Findings suggest that the inclusive, community-based SFL model is effective in engaging Shedders and facilitating positive and sustained changes in health and wellbeing outcomes. Using gender-specific approaches in the informal and safe environment of the Shed are effective in engaging men in structured health and wellbeing initiatives, particularly those who may be more vulnerable, isolated or lonely. Trial registration This study has been retrospectively registered with the ‘International Standard Randomised Controlled Trial Number’ registry (ISRCTN79921361) as of 05/03/2021.