Compassion-based interventions are a reasonably new therapeutic approach for enhancing mental wellbeing and have received a substantial level of research attention in recent years. These interventions aim to cultivate a sense of compassion in their recipients and there is a growing body of literature supporting their efficacy. Research efforts are now focusing on examining the effectiveness of compassion-based interventions in novel groups who are vulnerable to mental health concerns. In line with this, Part A of this thesis sought to systematically review the literature on the efficacy of compassion-based interventions for enhancing older adult wellbeing, adopting a narrative synthesis approach. Whilst it was found that the current evidence base is highly heterogenous and of modest quality, it was concluded that compassion-based interventions appear to have the potential to enhance various aspects of older adult wellbeing (e.g. low mood). Part B of this thesis presents an empirical study which examined the effectiveness of a brief, online compassionate imagery intervention for enhancing veterinarian mental wellbeing. The findings suggest that this innovative intervention can improve a range of wellbeing outcomes in this group, including resilience, self-reassurance and self-criticism.