Purpose Parent and therapist engagement and partnership are critical in early intervention physiotherapy and occupational therapy for infants with cerebral palsy to improve outcomes. The main aim of this study was to understand how parents perceive their engagement experience in early intervention over time. Methods Grounded theory methodology was used. Twenty parents of diverse backgrounds participated in 22 interviews (including some repeated longitudinally) to reflect on their engagement experience within the context of early intervention community services provided in the UK NHS. Results The findings highlight how parents’ perspectives of their engagement in EI change according to critical circumstances, including their preceding neonatal trauma, the at-risk CP label, firmer diagnosis of CP and their child’s response to intervention. We theorise that this disrupted transition experience to parenthood becomes part of parental framing (or sense-making) of their engagement in EI. Overlapping frames of uncertainty, pursuit and transformation capture and explain nuances in parents’ engagement patterns within EI over time. Conclusion This theorising has implications for early intervention therapists in how they engage in the lives of families and partner with parents to support healthier parental transition, wellbeing and subsequent improved infant outcomes.