<p>Society faces a growing burden of preventable health-related issues, highlighting the need for effective interventions that promote health and prevent illness, particularly among high-risk groups. The Five Ways to Wellbeing course is a 6-week intervention designed to enhance wellbeing and health by encouraging participants to practice five key activities: connect, be active, take notice, keep learning, and give. This study assessed changes in wellbeing, social connection, and health among participants facing physical and mental health challenges, following participation in the Five Ways to Wellbeing course, using a non-randomized, longitudinal, quasi-experimental design.&#xa0;A total of 373 adults who participated in the Five Ways to Wellbeing course were assessed at baseline, immediately after the intervention, and at 6- and 15-months post-intervention. Wellbeing, social connection, and physical and mental health were measured using validated questionnaires. A non-randomized comparison group (<i>n</i> = 923) from a separate study was included, as randomization was not possible. Changes over time and between groups were analyzed using paired t-tests and multilevel models.&#xa0;Participants reported significant improvements in wellbeing and social connection, sustained at 6 and 15 months (Cohen’s <i>d</i> = 0.21–0.63). Improvements in mental health were greater than in the comparison group, with statistically significant time-by-group interaction effects (<i>p</i> = 0.012 at post-test; <i>p</i> = 0.002 at 15 months). Improvements in physical health were comparable between groups (<i>p</i> = 0.206 and <i>p</i> = 0.107).&#xa0;The Five Ways to Wellbeing course may offer a promising approach to improving short- and long-term wellbeing, social connection, and subjective health in a group of vulnerable participants seeking to improve their health.</p>