BACKGROUND: Early years interventions are critical to children's health and development and are emerging as core to public health programmes in the UK and globally. Evaluating such interventions is complex. The study reported in this article evaluates a place-based public health initiative 'A Better Start Southend' (ABSS) aimed at facilitating early years' development specifically. It centres on examining the access barriers and facilitators experienced by parents and young children, as perceived by health professionals providing these services. METHODS: This paper illustrates the utilisation of participatory action research (PAR) approach, employing creative methods, including spider grams, service mapping and photovoice, with health professionals delivering ABSS services. PAR methods enabled exploration of community resources that facilitate or impede early childhood development in the local context. RESULTS: Operationalising PAR yielded critical providers' perspectives on key challenges of delivering these programmes, and the factors that in their view impeded their uptake by families and hence effectiveness. The approach provided space for authentic knowledge production through critical reflexive enquiry, exchange, collaborative dialogue and transformation. Through the process, participants revealed the social and commercial determinants of childhood development and how these determined the reach and success of ABSS. Health professionals especially highlighted poor-quality housing, poor public transport, the cost-of-living crisis and harmful commercial marketing practices as key barriers to promoting good early childhood development. System-wide barriers were also reported and included poor resourcing of health and social care services, lack of culturally and linguistically accessible provisions, and exclusionary practices creating inequitable access to health for many families and children. CONCLUSION: PAR is a potentially valuable tool for healthcare evaluations with the ability to generate nuanced reflexive perspectives and considerations that go beyond identifying the outcomes and gaps in interventions. It draws participants into a reflexive process to define pathways for change. Health professionals identified social inequities as the most significant barrier to promoting early childhood development. These inequities were not addressed in the design and implementation of the early year programme under study. The study supports the need for a multi-level, multi-systems and intersectional framework for place-based public health programmes to have the desired impact and reduce inequalities in access to early years interventions.