Background: After discharge from the intensive care unit, patients and relatives struggle to rebuild their lives while suffering from fatigue and distress. Intensive care unit diaries written by relatives are a novel approach that may help relatives and patients process the critical illness experience together. Objectives: To explore patients’ and relatives’ perceptions and use of a diary written by relatives for the critically ill patient. Design: Hermeneutical-phenomenological interview study. Setting: Two regional mixed surgical/medical intensive care units in a regional hospital. Participants: 10 critically ill patients and 13 relatives. All participants were 18 years or older, all patients had undergone mechanical ventilation. Methods: Dyadic, in-depth interviews conducted at 3–6 months and 8–16 months after discharge from the intensive care unit in 2015–2017. Interviews were analyzed using Ricoeur's theory of interpretation; a three-step process initiated by a naïve reading; followed by a structural analysis exploring the internal relations of the text, and finally, a critical interpretation to identify the most probable interpretation. Results: Before sharing the intensive care unit diary, relatives had to feel able to give the diary to the patient, which meant separating themselves from the diary and being available for discussions with the patient. Likewise, the patients had to be prepared to receive the diary and to acknowledge relatives’ efforts. Sharing the diary included interpreting the content of the diary, and developing a re-configured story based on the diary. Conclusion: The diary written by relatives for the critically ill patient was fulfilled when the diary was shared between the authoring relative and patient and a re-configured story was developed. This enabled a strengthened relationship between patient and relative. Not sharing could be disappointing to the relative, but did not preclude discussion of the experience of critical illness. This study provides professionals with knowledge about supporting patients and relatives through intensive care unit diaries written by relatives. Relatives need guidance on when to share the diary with the patient and how to accept patient rejection.