Objectives Opioid use among people who inject drugs can lead to serious complications, including infections. We sought to study trends in rates of these complications among people with an opioid use disorder (OUD) and the sequelae of those hospitalizations. Methods We analyzed all inpatient hospitalizations for serious infections (infective endocarditis [IE], spinal infections, nonvertebral bone infections, and skin or soft tissue infections) among people with OUD in Ontario between 2013 and 2019. We reported the population adjusted rate of hospitalizations for serious infections annually, stratified by type of infection and prevalence of prior opioid agonist therapy and hydromorphone prescribing. We reported characteristics of hospitalizations and 30–day mortality in the most recent 2 years. Results Among people with OUD there was a 167% increase in rates of IE (7.7-20.6 per million residents; P < 0.01), a 394% increase in rates of spinal infections (3.4–16.8 per million residents; P < 0.01), a 191% increase in rates of nonvertebral bone infections (8.9 to 25.9 per million residents; P < 0.01), and a 147% increase in infections of the skin or soft tissue (32.1–79.4 per million residents; P < 0.01) over 7 years in Ontario. Death in-hospital and within 30 days of discharge was highest among those with IE (11.5% and 15.9%, respectively), and lower among those with other infections (<5%). Conclusions Rates of serious infections among people with OUD are rising, placing a significant burden on patients. These findings suggest that early intervention and treatment of infections in this population are needed to prevent downstream harm.