BACKGROUND: Adapting co-creation research processes and/or public health interventions improves the fit between the intervention and population of interest, potentially resulting in more relevant and effective interventions. Mode 2 research approaches (e.g., co-creation, co-production, co-design, community-based participatory research, and participatory action research) can ensure that adaptations fit the socio-cultural and economic contexts. However, an overview of existing practices and how to co-adapt is lacking. This study aimed to provide an overview of the use of co-adaptation in co-creation processes and/or public health interventions. METHODS: We conducted a rapid review search on the Health CASCADE co-creation database. Relevant peer-reviewed studies reporting on co-adaptation of public health interventions were identified. A call for case studies via social media and co-authors' snowballing was issued to perform interviews with co-creation researchers gaining insights into how co-adaptation was applied from unpublished studies and practice. Interviews were analysed using template analysis. RESULTS: Fourteen studies addressed various public health issues by co-adapting co-creation processes, intervention activities, communication platforms, monitoring strategies, training components, and materials' language and tone. Most studies lacked detailed reporting on the co-adaptation process, though some provided information on group composition and number, duration, and methods applied. Two out of 14 studies used a framework (i.e., Intervention Mapping Adapt), seven described their adaptation procedure without naming a specific framework, and five did not report any procedures or frameworks. Five of seven case studies used adaptation frameworks (e.g., ADAPT guidance). Interviews provided insights into the co-adaptation process emphasising the importance of contextual fit, integrating prior knowledge, and logging adaptations. CONCLUSIONS: This study is the first introducing the concept of and exploring co-adaptation of co-creation processes and/or public health interventions. It provides details regarding adaptations made, whether and which frameworks were used, and procedures applied to adapt. The findings highlight the need for tailored frameworks for co-adaptation and better reporting of co-adaptation processes.