Objectives To estimate the frequency and characteristics of opioid prescribing by multiple providers in Medicare and the association with hospital admissions related to opioid use. Design Retrospective cohort study. Setting Database of prescription drugs and medical claims in 20% random sample of Medicare beneficiaries in 2010. Participants 1 808 355 Medicare beneficiaries who filled at least one prescription for an opioid from a pharmacy in 2010. Main outcome measures Proportion of beneficiaries who filled opioid prescriptions from multiple providers; proportion of these prescriptions that were concurrently supplied; adjusted rates of hospital admissions related to opioid use associated with multiple provider prescribing. Results Among 1 208 100 beneficiaries with an opioid prescription, 418 530 (34.6%) filled prescriptions from two providers, 171 420 (14.2%) from three providers, and 143 344 (11.9%) from four or more providers. Among beneficiaries with four or more opioid providers, 110 671 (77.2%) received concurrent opioid prescriptions from multiple providers, and the dominant provider prescribed less than half of the mean total prescriptions per beneficiary (7.9/15.2 prescriptions). Multiple provider prescribing was highest among beneficiaries who were also prescribed stimulants, non-narcotic analgesics, and central nervous system, neuromuscular, and antineoplastic drugs. Hospital admissions related to opioid use increased with multiple provider prescribing: the annual unadjusted rate of admission was 1.63% (95% confidence interval 1.58 to 1.67%) for beneficiaries with one provider, 2.08% (2.03% to 2.14%) for two providers, 2.87% (2.77% to 2.97%) for three providers, and 4.83% (4.70% to 4.96%) for four or more providers. Results were similar after covariate adjustment. Conclusions Concurrent opioid prescribing by multiple providers is common in Medicare patients and is associated with higher rates of hospital admission related to opioid use.