Background Early childhood is a critical period for the development of obesity, with new approaches to prevent obesity in this age group needed. We designed and piloted the 3 Pillars Study (3PS), a healthy lifestyle programme informed by attachment theory for parents of preschool-aged children. Methods A 2-arm, randomised controlled pilot study was conducted to assess the effectiveness of 3PS, a 6-week programme involving a half-day workshop plus 6-week access to a study website. The programme was designed to promote routines around healthy lifestyle behaviours, including sleep, limited screen use, and family meals, within the context of positive, reciprocal parent-child interactions. Parents (n = 54) of children aged 2-4 years who regularly exceeded screen use recommendations (�1 hour per day), were randomised to the 3PS programme (n = 27) or a wait-list control group (n = 27). Child screen time at 6 weeks was the primary endpoint. Frequency of family meals, parent feeding practices, diet quality, sleep, Child Routine Inventory (to assess predictability of commonly occurring routines), and household chaos were also assessed. Study data were collected online at baseline, 6 weeks, and 12 weeks via REDCap.