This single-blind, pragmatic, cluster randomised controlled trial aims to investigate uptake of children's weight management services in response to enhanced National Child Measurement Programme (NCMP) letters providing weight status feedback to parents in three English counties in 2015. Parents of 2642 overweight or very overweight (obese) children aged 10-11 years received an intervention or control letter informing them of their child's weight status. Intervention letters included (i) a visual tool to help weight status recognition, (ii) a social norms statement, and for very overweight children, (iii) a prepopulated booking form for weight management services. The primary outcome was weight management service enrolment. Additional outcome measures included attendance at and contact made with weight management services, and a number of self-report variables. A small effect was observed, with intervention parents being significantly more likely to enrol their children in weight management services (4.33% of Intervention group) than control parents (2.19% of Control group) in both unadjusted (OR = 2.08, p = .008) and adjusted analyses (AOR = 2.48, p = .001). A similar picture emerged for contact with services (4.80% Intervention vs. 2.41% Control; OR = 2.10, p= .003; AOR = 2.46, p< .001) and attendance at services, although group differences in the latter measure were not significant after corrections for multiple comparisons (1.89% Intervention vs. 1.02% Control; AOR = 2.11, p = .047). No effects were found on self-report variables. Theoretically informed weight status feedback letters appear to be an effective strategy to improve enrolment in paediatric weight management services.