AIMS: The risk of surgical site infection (SSI) in hand trauma surgery is estimated to be approximately 5% to 10%. However, the severity of these SSIs remains unclear. We aimed to determine the risk of deep SSI, septic arthritis, and osteomyelitis following hand trauma surgery using Hospital Episode Statistics data, a source of routinely collected national healthcare data in England. METHODS: This was a national cohort study of hand trauma surgery in the NHS in England over 22 years, split into four sub-cohorts of the most common hand trauma operations: hand fracture fixation; flexor tendon repair; extensor tendon repair; and nerve repair. The primary outcome was readmission for deep SSI, septic arthritis, or osteomyelitis following hand trauma surgery at 30 and 90 days. RESULTS: There were 280,747 cases across the study period. A total of 4,013 postoperative infections, including deep SSI, septic arthritis, and osteomyelitis, occurred by 30 days, and 5,563 by 90 days. This corresponds to a severe SSI risk of 1.4% (95% CI 1.4 to 1.5) by 30 days and 2.0% (95% CI 1.9 to 2.0) by 90 days following common hand trauma surgery. Data for each cohort indicated a higher risk of osteomyelitis in fracture fixation and a higher risk of deep SSI in soft-tissue reconstruction. CONCLUSION: The risk of readmission for deep SSI, septic arthritis, or osteomyelitis following hand trauma surgery is 1.4% at 30 days, rising to 2% at 90 days. These data can be used to inform patients of their risk and to guide future research in hand trauma surgery.