Peer support is a widely used intervention that offers information and emotional support to parents during their infant's admission to the neonatal unit and/or post-discharge. Despite its widespread use, there are no comprehensive insights into the nature and types of neonatal-related peer support, or the training and support offered to peer supporters. We aimed to bridge these knowledge gaps via an international study into neonatal peer support provision. A mixed-methods study comprising an online survey was issued to peer support services/organisations, and follow-up interviews held with a purposive sample of survey respondents. Survey/interview questions explored the funding, types of peer support and the recruitment, training and support for peer supporters. Descriptive and thematic analysis was undertaken. Thirty-one managers/coordinators/trainers and 77 peer supporters completed the survey from 48 peer support organisations/services in 16 different countries; with 26 interviews undertaken with 27 survey respondents. We integrated survey and interview findings into five themes: 'background and infrastructure of peer support services', 'timing, location and nature of peer support', 'recruitment and suitability of peer supporters', 'training provision' and 'professional and emotional support'. Findings highlight variations in the types of peer support provided, training and development opportunities, supervisory and mentoring arrangements and the methods of recruitment and support for peer supporters; with these differences largely related to the size, funding, multidisciplinary involvement, and level of integration of peer support within healthcare pathways and contexts. Despite challenges, promising strategies were reported across the different services to inform macro (e.g. to facilitate management and leadership support), meso (e.g. to help embed peer support in practice) and micro (e.g. to improve training, supervision and support of peer supporters) recommendations to underpin the operationalisation and delivery of PS provision.