AbstractThe employment of mental health peer support (PS) is recommended in national and international mental health policy, and widely implemented across many countries. The key components of PS remain to be identified. This study aimed to develop a typology of components involved in one-to-one PS for adults in mental health services. A systematised review was performed to establish a preliminary long list of candidate components, followed by expert consultation (n = 21) to refine the list. Forty-two publications were full-text reviewed, comprising 26 trial reports, nine training manuals, and seven change model papers. Two hundred forty-two candidate components were identified, which were thematically synthesised to 16 components and eight sub-components, categorised into four themes: recruitment, preparation, practice, and PS worker wellbeing. Our typology can inform reflection and planning of PS practice, and allow more rigorous and synthesised studies, such as component network meta-analyses, to characterise the impact of each component and their interactions.