Due to the growing elderly population, adult children care-givers (ACCs) are increasingly providing complex care for one or both elderly parents. Social support from similar peers can mitigate care-giving-related health declines. To date, ‘peer similarity’ amongst care-givers has been predominantly investigated in the context of peer-matching interventions. However, because peer similarity is especially influential in ‘naturally occurring’ support networks, care-givers' everyday peer support engagement warrants further attention. Our goal was to explore care-givers' everyday peer support engagement and the influence of peer similarity on support perceptions. We employed a mixed-method design using Web-based surveys and in-depth qualitative interviews. The quantitative data were analysed using a hierarchical multiple while qualitative data were thematically analysed. Seventy-one ACCs completed the online questionnaire and 15 participated in a telephone interview. Peer similarity was positively and significantly associated with perceived support (β = 0.469, p < 0.0005) and explained 18.5 per cent of the additional variance. ACCs' narratives suggested the most important aspect of similarity was ‘shared care-giving experience’ as it optimised the support received from peers, and also enhanced the quality of the relationship. In conclusion, both data-sets underscored that peer similarity importantly influences support perceptions. The importance of ‘shared care-giving experience’ suggests that a more comprehensive understanding of this concept is needed to optimise peer-matching endeavours. Peer similarity's influence on relationship quality should also be explored.