Background: There are marked disparities between pre-school children in key skills affecting school readiness, disparities that commonly persist and influence children's later academic achievements, employment, and adjustment. Much of this disparity is linked to socio-economic disadvantage and its impact on the home learning environment. Children's Centres are an ideal context in which to implement and evaluate programmes to address this problem. They principally serve the 30% worst areas on the Indices of Deprivation Affecting Children, providing for families from the antenatal period up to age 5 years, aiming to promote parenting skills and provide care for children. Methods: We are conducting a randomised controlled trial, based in Children Centres, to evaluate a parenting intervention for caregivers of children between 28 and 45 months of age. The intervention provides training to parents in dialogic book-sharing. The training is run by a facilitator who sees parents in small groups, on a weekly basis over 7 weeks. The study is a cluster randomised controlled trial. Twelve of the Children's Centres in the town of Reading in the UK have been randomly assigned to an index or control condition. The primary outcome is child cognition (language, attention, and executive function); and secondary outcomes are child social development, behaviour problems, and emotion regulation, parenting during book-sharing and problem solving and parental child behaviour management strategies. Data are collected at baseline, post-intervention and 4-6 months post-intervention. Discussion: The Impact of Early-years Provision in Children's Centres trial (EPICC) aims to evaluate the impact of an early parenting intervention on several key risk factors for compromised child development, including aspects of parenting and child cognition, social development, behaviour problems and emotion regulation. The study is being carried out in Children's Centres, which largely serve the most disadvantaged families in the UK. Since the intervention is brief and, with modest levels of training, readily deliverable within Children's Centres and similar early childcare provision centres, demonstration that it is of benefit to child cognition, socio-emotional development and behaviour would be important.