Background: Diaries written for patients in the intensive care unit (ICU) are offered in many European countries. In Austria, ICU diaries have been relatively unknown, but since 2012, they have started to emerge. Aim: The aim of this study was to explore the extent and application of ICU diaries in Austria in 2015. Method: The study had a prospective multiple methods design of survey and interviews. All ICUs in Austria were surveyed in 2015 to identify which ICUs used diaries. ICUs using diaries were selected for semi-structured key-informant telephone interviews on the application of ICU diaries. Interviews were analysed by content analysis. Results: Of the 178 ICUs contacted, 13 had implemented ICU diaries. In all ICUs, diaries were sporadically introduced by a few dedicated nurses. Experiences of participating nurses can be summarized in two main themes: (a) the process of innovation and (b) the process of practice. Sub-themes were: (i) inspiration, creativity and innovation and (ii) purpose, indications, responsibility, authorship, experience, negative reception, and post-ICU practice. Individual nurses at each ICU found ways to organize and format ICU diaries while dealing with ambivalence and legal implications. Conclusion: The implementation of a new nursing intervention is an ongoing process. Being innovative and responsible can be challenging, especially in hierarchical team structures. We recommend that nurses work towards national standards for the diary concept in order to enable future research into the process and outcome of ICU diaries. Relevance to Clinical Practice: The implementation of ICU diaries in routine care requires an ongoing adaptive, reflective process. Nurses may experience innovation, leading to the development of their own, feasible adaptions and structures.