Necrotizing fasciitis is a rare but severe soft tissue infection, and its diagnosis is difficult and often delayed. Immediate treatment comprising extensive debridement, highly dosed broad-spectrum antibiotic therapy and intensive care is necessary to prevent fatal outcomes. Considering the global rise in overweight patients and the known negative effects of obesity on the immune system, the aim of this study was to analyze whether overweight results in a more severe course of necrotizing fasciitis, worse outcomes and an increased mortality rate among overweight patients compared than in normal weight patients. The present study involved a retrospective analysis of 29 patients who were treated for necrotizing fasciitis in our level one trauma center during the eight-year period between 2013 and 2020. Based on their BMIs, the patients were assigned to either the overweight group (BMI > 25) or the normal weight group. In the study population, being overweight appeared to be a predictor for a more severe course of necrotizing fasciitis. Overweight patients suffered from sepsis significantly more often than normal weight patients (13 vs. 5; p = 0.027). Furthermore, they were dependent on invasive ventilation (26.6 ± 33.8 vs. 5.9 ± 11.9 days; p = 0.046) as well as catecholamine support (18.4 ± 23.7 vs. 3.6 ± 5.7 days; p = 0.039) for significantly longer. Necrotizing fasciitis remains a challenging and potentially fatal disease. Within the patient collective, the severity of the disease and treatment effort were increased among overweight patients.