Aim To assess the fidelity of delivery of NHS Health Checks in general practice. Design and Setting Fidelity assessment of video/audio recordings of NHS Health Check consultations conducted in four GP practices across the East of England. Method A secondary analysis of 38 NHS Health Check consultations video or audio recorded as part of a pilot study of introducing discussions surrounding cancer risk into NHS Health Checks. Using a checklist based on the NHS Health Check Best Practice Guidance, fidelity of delivery was assessed as the proportion of key elements completed during the consultations. Results The mean number of elements of the NHS Health Check completed across all consultations was 14.5/18 (80.3%), with a range of 10-17 (55.6-94.4%). The mean fidelity for risk assessment, risk communication and risk management sections was 8.7/10 (86.8%), 4.1/5 (81.6%) and 1.7/3 (56.1%) respectively. Elements with the lowest fidelity were ethnicity assessment (31.6%), family history of cardiovascular disease assessment (65.8%), AUDIT-C communication (34.2%) and dementia risk management (15.8%). Conclusion Although fidelity of delivery was high overall, important elements of the NHS Health Check were being regularly omitted. Opportunities for behaviour change, particularly relating to alcohol consumption and dementia risk management, may be being missed.