Introduction. Engagement with life is central to ageing well. There is currently a lack of flexible programs for promoting engagement that tailor to the unique interests, capacities, and life circumstances of individuals. We designed and evaluated a new program for promoting engagement with later life based on principles of behavioral activation. Methods. A total of 135 adults aged 65 and older who scored at or below the median on the Life Engagement Test were randomly assigned to either a 6-week behavioral activation program (n = 69); or a 6-week well-being program based on brief positive psychology interventions (the active control; n = 66). Participants completed assessments at baseline, 1-week follow-up and 3-month follow-up. The primary outcome was engagement with life, and secondary outcome measures included social network characteristics, measures of mental health, well-being, and psychological and self-regulatory resources. Results. Participants in both conditions showed improvements in engagement with life post-intervention that were sustained at 3-months. Post-intervention improvements in both conditions were observed across most secondary outcomes; however, for several outcomes, participants with more limited functional and cognitive resources benefitted from participation in the positive psychology (active control) condition, but not the treatment condition. Conclusion. Similar levels of improvement in engagement with life and well-being were evident for participants who completed a behavioral activation-focused intervention, compared with participants who completed a positive psychology focused intervention. The positive psychology approach may confer greater benefits for emotional well-being among those with poorer functional and cognitive abilities.