Background: Exercise referral schemes (ERSs) within clinical populations offer inactive individuals the opportunity to increase physical activity levels over the length of scheme. Schemes are also intended to support the treatment of specific health conditions of medically referred individuals through increased physical activity behaviours. The extant literature concerning the impact of exercise referral on physical activity levels is inconsistent. It is of interest researchers, policy makers, commissioners and practitioners to to consider broadly whether meaningful change in physical activity levels are observed in people who undergo exercise referral, to identify potential effective policy actions in supporting active living. Purpose: To examine if ERSs increase physical activity levels in a large cohort of individuals throughout England, Scotland and Wales from The National Referral Database. Method: Data were obtained from 5246 participants from 12 different referral schemes. Average age was 53±15 years and, 68% of participants were female. Participants self-reported International Physical Activity Questionnaire (IPAQ) scores pre- and post- scheme, to determine if exercise referral had any impact on change in physical activity levels. Two stage individual patient data meta-analysis was performed on the both pre-ERS, and change scores, (i.e. post- minus pre-ERS scores) for MET-minutes/week calculated from IPAQ. Analyses were conducted on the continuous data collected using the IPAQ. Results: For pre-ERS MET-minutes/week the estimate and 95%CI from random effects model was 676 MET-minutes/week [539 to 812 minutes]. For change in MET-minutes/week the estimate and 95%CI from random effects model for was an increase of 540 MET-minutes/week [396 to 684 minutes]. Significant heterogeneity was evident among the schemes (I2 > 80%). Changes in total PA levels occurred as a result of increases in vigorous activity of 17 minutes [95%CI 9 to 24 minutes], increases in moderate activity of 29 minutes [95%CI 22 to 36 minutes], and reductions in sitting of -61 minutes [95%CI -78 to -43 minutes], though little change in walking (-5 minutes [95%CI -14 to 5 minutes]). Conclusion: Observation of participants undergoing ERSs suggests that most are already âmoderately activeâ upon entering an ERS. Changes in physical activity behaviour associated with ERS participation were varied and primarily facilitated by increased moderate-to-vigorous physical activity and reduced sitting. However, this was not sufficient to result in IPAQ categorical change and participants where thus on average still classed as âmoderately activeâ. Further work is required to ensure ERSs are implemented to targeting the appropriate populations where they may result in the greatest benefit.