AIM: To develop consensus on a core set of standardized outcome measures to be applied to each domain of the previously developed core outcome set for lower limb orthopaedic surgery for ambulant children with cerebral palsy (CP). METHOD: This work consisted of the following three steps: (1) a scoping review of the literature to identify previously used outcome measures to assess lower limb orthopaedic surgery of ambulant children with CP; (2) searching the COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) and PubMed databases to assess the quality of the psychometric properties of outcome measures and feasibility criteria; and (3) a consensus meeting with seven healthcare professionals with expertise in CP research and in the assessment of outcome measure psychometric properties was held in September 2021. Consensus on the outcome measures core set was developed through presentation of the evidence and whole-group discussions. RESULTS: A combination of clinician-driven and patient-reported outcome measures was considered the most appropriate way to assess the outcome of orthopaedic surgical interventions. Agreement was reached on seven core outcome measures: three-dimensional gait analysis, Edinburgh Visual Gait Scale, Gross Motor Function Measure, Gait Outcome Assessment List, Gillette Functional Assessment Questionnaire, Patient-Reported Outcome Measure Instrument System (pain interference, and fatigue), and Cerebral Palsy Quality of Life for Children questionnaire. INTERPRETATION: This study recommends a set of core outcome measures for use in research on lower limb orthopaedic surgery for ambulant children with CP. Consistent use of this core set would enhance validity and comparability of future research.