Objective <p>Descending necrotizing mediastinitis (DNM) is a life-threatening infection that causes by cervical infections. An appropriate diagnosis and surgery are critical for improving outcomes. We retrospectively analyzed 37 surgically treated patients over a 20-year period to identify factors associated with improved survival and prolonged hospitalization.</p> Methods <p>Patients who underwent combined cervical and thoracic drainage for DNM at our institution in 2004–2024 were reviewed. Clinical data, surgical approaches, outcomes, and risk factors for long-term hospitalization were analyzed.</p> Results <p>The cohort (<i>n</i> = 37) included 22 males (59.5%), with a mean age of 64.1 years. Endo’s classification was type IIB (extension to the lower posterior mediastinum) in 28 cases. Bilateral thoracotomy (including VATS) was performed in 23 patients (mean time from onset to surgery: 5.8 days). The median ICU and hospital stays was 20.9 and 59.3 days, respectively. The 90-day mortality rate was 8.1% (<i>n</i> = 3). All non-survivors were elderly and had renal impairment at admission. Among 34 survivors, a multivariate analysis identified age (<i>p</i> = 0.0012), odontogenic origin (<i>p</i> = 0.0305), and drainage duration (<i>p</i> = 0.0047) as independent predictors of prolonged hospitalization. Notably, 72.2% of short-stay patients were treated within the last 10 years, indicating improved outcomes.</p> Conclusion <p><i>Our 20-year experience suggests elderly patients with renal impairment were at high risk of early mortality. In survivors</i>,<i> age</i>,<i> odontogenic origin</i>,<i> and drainage duration predicted prolonged hospitalization.</i> Future efforts should focus on minimizing the hospitalization duration while maintaining effective infection control.</p>