Background: Informal caregivers face risks of social isolation. Given the high prevalence of informal caregivers in Europe, a considerable proportion of the population are also former caregivers. The Finnish Expert Caregiver intervention sought to train former caregivers to become volunteers aim-ing to support current caregivers through mainly peer support. Objectives and methods: The aims of this mixed method non-controlled exploratory intervention study were to assess the feasibility of the Finnish Expert Caregiver intervention by co-designing and implementing the intervention, and by assessing demand and practicality with special attention to the impact of COVID-19. Results: The findings imply that the intervention was feasible as it resulted in a co-designed training course consisting of 30 h with 25 participants enrolling and 19 of them trying volunteering activities. The participants reported high scores on well-being at all timepoints of study, however, without statistically significant differences. The analysis of the focus group interviews revealed that the Expert Caregivers experienced the intervention as meaningful and offered them a sense of belonging with the other participants. Apart from using their caregiving past as an asset, the participants also took advantage of other personal skills and resources. Risks of adverse effects were related to the participants’ expectations on their own contribution, demanding peer support recipients, poorly functioning peer support groups, and insufficient distance to one’s caregiving past. The participants stressed the need for continuing support from intervention facilitators. Conclusions: Future studies with larger samples should investigate whether the effects differ between subgroups of participants and explore the perspective of the peer support recipients.