Abstract Few studies all based on classical surveys have provided prevalence estimates of chronic pain (CP) in opioid-maintained patients (OMPs) but often had a limited patient sample size and a great variability in the prevalence estimates. This study sought to assess the prevalence of CP in the exhaustive population of OMPs using the capture–recapture method applied to the French nationwide health care database. Capture–recapture methods are increasingly used to estimate the prevalence of chronic conditions but have never been used in the specific context of CP in OMPs. Three large medical-administrative sources were used: the prescription drug database (A-list), the national hospital discharge database (M-list), and the pain center database (C-list). Between 2015 and 2016, 160,429 OMPs aged 15 years and older were identified and age- and sex-matched with 160,429 non-OMPs. All patients treated with analgesic drugs for ≥6 months (A-list) or diagnosed with CP (M- and C-list) were included. Capture–recapture analyses were performed to yield CP estimates with their 95% confidence intervals using log-linear models. In 2015 to 2016, 12,765 OMPs and 2938 non-OMPs with CP were captured. Most patients were male (67%) in OMPs and non-OMPs; median ages for OMPs and non-OMPs were 46 (interquartile range: 38-51) and 48 (41-53) years, respectively. The CP prevalence estimated in OMPs and non-OMPs ranged from 23.6% (14.9-46.2) to 32.1% (28.6-36.3) and from 7.28% (3.98-18.4) to 9.32% (7.42-12.1), respectively. This first study on CP in the exhaustive population of OMPs using the capture–recapture method demonstrated a high prevalence of CP in OMPs, 3- to 4-fold than in the general population.