INTRODUCTION: Day-case surgical activity is increasing in the UK yet there is a lack of data on the prevalence of chronic post-surgical pain in this population. This study uses data from the POPPY study to estimate the prevalence of chronic post-surgical pain after day-case surgery, its relationship with quality of life and also explores associated factors. METHODS: Data were collected from eligible consenting adults having day-case surgery in 199 sites across the UK. Baseline data were collected on the day of surgery, and patients were followed up by short message service-delivered questionnaires on day 1, day 3, day 7 and day 97. Chronic post-surgical pain was defined using pain severity scores at day 97. Multivariable logistic regression models were used to explore associations with chronic post-surgical pain. RESULTS: At day 97, 3442 patients had responded from a total of 7839 recruited. The estimated prevalence of chronic post-surgical pain was 7.2% (95%CI 6.4-8.1%). We found the following were associated with chronic post-surgical pain: week 1 pain scores; orthopaedic, breast and plastic surgical specialities; non-surgical site chronic pain at baseline; deprivation; and ethnicity. Patients with chronic post-surgical pain had a mean (SD) decrease of 0.137 (0.205) in health-related quality of life score compared with baseline. DISCUSSION: This is the first large UK multicentre, prospective observational study exploring chronic post-surgical pain after day-case surgery. Multivariable modelling highlighted several associated factors. Chronic post-surgical pain is common after day-case surgery and is associated with reduced quality of life.