Importance Previous research suggests that patients with hidradenitis suppurativa (HS) may face a higher risk of serious infections compared with those with psoriasis. However, these studies are subject to limitations that could constrain their reliability. Objective To compare the risk of hospitalization from noncutaneous infections, infection profiles, and the length of stay (LOS) of adult patients with HS and psoriasis treated with adalimumab. Design, Setting, and Participants This retrospective cohort study was conducted using deidentified claims data from the MarketScan database. All adult patients with HS or psoriasis who initiated adalimumab therapy between January 2017 and December 2020 were included. Data were analyzed from October 2023 to March 2024. Exposures New users of adalimumab diagnosed with psoriasis or HS, identified using International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes and adalimumab prescriptions. Main Outcomes and Measures The primary outcome was hospitalization from noncutaneous infections in a time-to-event analysis using inverse probability weighting to account for confounders in the Cox regression models. Secondary outcomes included the infection types compared using incidence rate ratios and LOS analyzed with multivariable Poisson regression. Results Of 10 349 included patients, 5641 (54.5%) were female, and the mean (SD) age was 44.8 (12.8) years. The cohort included 1650 patients with HS and 8699 with psoriasis. The HS cohort was younger (mean [SD] age, 36.2 [11.5] years vs 46.5 [12.4] years) and predominantly female (1271 [77.0%] vs 4370 [50.2%]), with higher rates of obesity, Crohn disease, anxiety, and depression. The weighted Cox analysis indicated an increased risk of serious infection in patients with HS (hazard ratio, 1.53; 95% CI, 1.34-1.86). This group also had a higher likelihood of sepsis and genitourinary infections (sepsis: incidence rate ratio, 2.07; 95% CI, 1.35-3.12; genitourinary infections: incidence rate ratio, 2.22; 95% CI, 1.22-3.86) and greater odds of prolonged LOS (odds ratio, 1.28; 95% CI, 1.13-1.45) compared with the psoriasis cohort. Conclusions and Relevance In this cohort study, among adults treated with adalimumab, those with moderate to severe HS had an elevated risk of infection and different infection profiles compared with those with psoriasis. Future research should focus on the impacts of disease severity and treatment regimens on infection risk and develop targeted prevention strategies.