Habit formation is an important goal for behaviour change interventions because habitual behaviours are elicited automatically and are therefore likely to be maintained. This study documented experiences of habit development in 10 participants enrolled on a weight loss intervention explicitly based on habit-formation principles. Thematic analysis revealed three themes: Strategies used to support initial engagement in a novel behaviour; development of behavioural automaticity; and selecting effective cues to support repeated behaviour. Results showed that behaviour change was initially experienced as cognitively effortful but as automaticity increased, enactment became easier. Habits were typically formed in work-based contexts. Weekends and vacations temporarily disrupted performance due to absence of associated cues, but habits were reinstated on return to work. Implications for theory and practice are discussed.