Background: This study looked to investigate the sometimes conscious and sometimes intuitive decision-making processes of Intensive Interaction practitioners. More specifically, this study set out to develop a rich description of how practitioners make judgements when developing a dynamic repertoire of Intensive Interaction strategies with people with severe or profound learning difficulties and/or autism, how this decision-making process is enacted in practice and what issues inform such decisions. Materials and Methods: This research followed a "Template Analysis" qualitative methodology, informed by semi-structured interviews with 13 experienced Intensive Interaction Practitioners (who had completed the Intensive Interaction Coordinators course as administered by the Intensive Interaction Institute). The participants included the following: speech and language therapists, parents, teachers, residential care staff and managers, and a clinical psychologist. Results: The findings of this study indicate why and how certain decisions are made by experienced practitioners before, during and after engagement in Intensive Interaction. Such decision-making is indicated as sometimes being intuitive in nature, sometimes more conscious, sometimes moving between the two cognitive states as differing issues arise. Practitioner decision-making was focused on a number of issues, including specific learning or care "agendas"; practitioner confidence and knowledge; environmental considerations; individual learner characteristics and behaviour; learner attention, "attunement" and arousal levels; building a shared "repertoire"; and issues of available time. Conclusions: The issue of how novice Intensive Interaction practitioners may best be supported to more quickly and confidently develop improved Intensive Interaction practices is discussed, proposing the development of a cyclical process of experiential learning and supported reflection.