Peer mentors may offer distinctive forms of support to people with advanced cancer. Whilst peer mentor programmes are known, little is understood about recruiting and training peer mentors to support those with advanced cancer. The purpose of this study is to determine the feasibility of recruiting and training peer mentors for a novel peer mentor intervention to promote well-being in people with advanced cancer. Feasibility study testing proactive introduction to a trained peer mentor for 12 weeks in the context of a randomized controlled two-arm trial and nested qualitative process evaluation was used. Peer mentors have/had cancer, recruited via an open call. Two-day training included a new bespoke module on coping with cancer. Descriptive recruitment and training data were captured, supplemented by qualitative interviews, analysed thematically. Forty-eight people expressed interest, mostly female (69%), with breast cancer (32%), and recruited via social media (49%). Twelve people completed training, with attrition often due to availability or mentors’ own health; many had advanced cancer themselves. They wanted to ‘give something back’, but also formed supportive bonds with fellow mentors. It is feasible to recruit and train people with lived experience of cancer to be peer mentors, but those with particular characteristics may predominate. Broad social media based recruitment may have merit in widening the pool of potential peer mentors.