The involvement of patients or next of kin (P/N) after a serious adverse event (SAE) is evolving. Beyond providing mandatory information, there is growing recognition of the need to incorporate their interests. This study explores practical manifestations of P/N involvement and identifies significant considerations for hospitals. The data collection involved various qualitative research methods: 7 focus groups with 56 professionals from 37 hospitals, an interview with 2 representatives from the Dutch Association of Hospitals, and an interactive reflection seminar with over 60 participants from 34 hospitals. Before the focus groups, a brief questionnaire was sent out to survey participants' practices regarding into SAE investigations. After the study, another questionnaire was distributed to gather suggestions for future improvements and to identify their lessons learned. Thematic analysis was applied to the gathered data to identify key themes. Hospitals are increasingly acknowledging the interests and perspectives of P/N, recognizing their potential contributions to organizational learning and improvement. P/N involvement following SAEs includes active participation in different stages of the investigation process, not just passive information dissemination. Important factors influencing involvement are the provision of (emotional) support, identification of needs, and transparency of the SAE investigation. This study enhances understanding of evolving practices surrounding P/N involvement in the context of SAEs in Dutch hospitals. The findings highlight the importance of promoting meaningful involvement, recognizing the significance of P/N experiences, and fostering a culture of transparency and collaboration. By examining the dynamics of involvement, this research aims to inform policy development and facilitate the implementation of patient-centered approaches to post-SAE care.