The National Health Service Health Check (NHS HC) is a population level public health programme. It is a primary prevention initiative offering cardiovascular risk assessment and management for adults aged 40-74 years (every five years). It was designed to reduce the incidence of major vascular disease events by preventing or delaying the onset of diabetes, heart and kidney disease, stroke and vascular dementia . Effectiveness of the programme has been modelled on a national uptake of 75% however in 2012/13 uptake, nationally, was 49%. Ensuring a high percentage of those offered an NHS HC actually receive one is key to optimising the clinical and cost effectiveness of the programme. A pragmatic quasi-randomised controlled trial was conducted in four general practitioner practices in Medway, England with randomisation of 3511 patients. The aim was to compare attendance at the NHS HC using the standard national invitation template letter (control) compared to an enhanced invitation letter using insights from behavioural science (intervention). The intervention letter includes i) simplification - reducing letter content for less effortful processing ii) behavioural instruction - action focused language iii) personal salience - appointment due rather than invited and iv) addressing implementation intentions with a tear off slip to record the date, time and location of the appointment. Logistic Regression explored the association between control and intervention group and attendance at a health check. 29.3% of patients who received the control letter and 33.5% of those who received the intervention letter attended their NHS HC (adjusted odds ratio 1.26, 95% confidence interval 1.09-1.47, p < 0.01). This was an absolute difference in uptake of 4.2 percentage points for those receiving the intervention letter. An invitation letter applying behavioural insights was more effective than the existing national template letter at encouraging attendance at an NHS HC. Making small, no cost behaviourally informed changes to letter invitations can improve uptake of the NHS HC. Further research is required to replicate the effect with more robust methodology and powered for sub-group analysis including socio-economic status. Current Controlled Trials ISRCTN66757664 , date of registration 28/3/2014.