Objective: The aim of the present study was to evaluate the hospital length of stay (LoS) and its associated factors among adult patients hospitalized with depression in Germany. Methods: This cross-sectional study included all adults (≥18 years) hospitalized with depression from January 2019 to December 2023 treated in 36 hospitals across Germany. The primary outcome was patients’ hospital LoS in days. The associations between age, sex, depression severity, co-diagnoses, hospital, and hospital LoS were analyzed using hierarchical multivariable linear regression models. Results: A total of 6579 patients (mean age 46.6 ± 17.7 years) with 8965 hospitalizations for depression were available. The mean hospital LoS was 35.2 days. Severe depression (+4.9 days) was associated with a longer hospital LoS, with moderate depression as the reference. Older age was positively associated with a longer hospital LoS. Vitamin D deficiency (+9 days), lipid metabolism disorders (+8 days), obesity (+8 days), sleep disorders (+7 days), and reaction to severe stress and adjustment disorders (+5 days) were also significantly associated with hospital LoS. Conclusions: In patients with depression, higher depression severity, advanced age, vitamin D deficiency, lipid metabolism disorders, obesity, sleep disorders, reactions to severe stress, and adjustment disorders were associated with a longer hospital LoS. Addressing these factors through comprehensive and integrated care strategies could help optimize hospitalization duration and improve overall patient outcomes.