Background: Guidance and principles for involving the public in research or service planning exist but are not specific to the needs of parents of children with life-limiting conditions or bereaved parents., Aim: Review the evidence on involving parents of children with life-limiting conditions and bereaved parents in research, service planning and advocacy, and use this to develop best practice guidance., Methods: Rapid review following the Cochrane Rapid Reviews Methods Group Guidance. MEDLINE and EMBASE were searched for primary studies of any design and literature/systematic reviews, and grey literature searching was conducted. Sources reporting on involving parents of children with life-limiting conditions or bereaved parents in healthcare, research, or charity work in any setting, were included. Data were charted using the UK standards for public involvement in research (PPI). Two PPI consultation workshops were conducted with parents (n = 13) and healthcare professionals/charity representatives (n = 7)., Results: Six sources were included. Four reported benefits of parental involvement and two reported burdens. In relation to best practice, two reported on the importance of inclusive opportunities, three on working together, four on support and learning, three on communications, one on impact, and one on governance. PPI consultation workshops highlighted new factors which were not present in the literature around communication and understanding the impact of involvement., Conclusion: Organisations working with this group should consider offering inclusive approaches to improve diversity, levelling power imbalances, ensuring flexibility of approach, and appropriate communication and impact., Patient or Public Contribution: The study was conducted in collaboration with 13 parents of children with life-limiting conditions and bereaved parents, and seven palliative care professionals. The group were involved at key stages of the review and contributed to the development of the findings and conduct of the review., (© 2024 The Author(s). Health Expectations published by John Wiley & Sons Ltd.)