To explore the lived experience of donors and recipients involved in peer-to-peer human milk donation. An exploratory descriptive qualitative study. Semi-structured interviews were conducted between November 2022 and April 2023. A total of 50 women consisting of 34 donors and 16 recipients were recruited using purposive sampling from specific social media groups in Hong Kong that focus on breast milk donation and sharing. Data were analysed based on thematic analysis. Five key themes were identified in this study: Motivation; Milk sharing as a social act; Not a Norm; Recommendation to formal milk banks; and Formal donation as the preferred route. The findings indicate informal milk sharing is seen as an inferior alternative to formal milk donation systems. The establishment of formal milk banks is viewed as a way to address the shortcomings of informal sharing. The findings have implications for the healthcare field, particularly in improving the experiences of those involved in informal milk sharing. The insights gained from the experiences of informal milk sharers can directly inform and enhance the services provided by formal milk banks. Given the growing prevalence of online informal milk sharing, healthcare professionals should enhance their understanding of this practice. However, the practice has remained understudied, particularly in Asian region. This study brings together the experiences of both milk donors and recipients, providing a comprehensive view on the phenomenon. The Standards for Reporting Qualitative Research (SRQR). No patient or public contribution.