Qualitative digital diary methods are a promising tool for capturing participants’ experiences in their own words and over time. The use of smartphone apps to collect this kind of data provides an accessible and flexible way to participate in research, but to truly benefit from this method, participants needs and preferences must be taken into account. This paper explores participants’ experiences of taking part in qualitative digital diary research, and highlights participants’ values and priorities for qualitative digital diary mental health research. Participants from two qualitative digital diary studies provided feedback on their experiences, in the form of interviews and focus groups, and data were analysed using reflexive thematic analysis. The two participant groups, people with lived experience of eating disorders, and young people from diverse backgrounds across London schools, allowed exploration of experiences across different contexts and populations. The six resulting themes each reflect a core value that participants identified as an essential component for them in qualitative digital diary research: Self-expression, flexibility, non-judgement, open communication, helpful reflection, and meaningful impact. Themes each highlight aspects of participants’ experiences that must be taken into account for future research to ensure that participants can take part in this type of research in ways that are meaningful to them, as well as most beneficial to the research. This paper provides an overview of participant experiences of qualitative digital diary research, and provides a framework for centring participant values and preferences in future qualitative diary research.