To analyze process and outcome quality of inpatient depression treatment depending on German language proficiency. Documentation of patients in 24 psychiatric hospitals in Baden-Württemberg (South Germany). The following three groups were matched according to age, gender, and education: native German speakers, non-native speakers with good German proficiency, and non-native speakers with limited German proficiency (67 in each group). Germans received more group psychotherapy than the other two groups (p = .003). No differences were found regarding pharmacotherapy. Non-native speakers with limited German proficiency were discharged an average of 19 days earlier than German speakers and 7 days earlier than non-native speakers with good German proficiency (p = .02). Compared to Germans, twice as many non-native patients with good German proficiency and nearly four times as many patients with limited German proficiency were discharged with depressive symptoms (p = .006). Results confirm the significance of linguistic factors for the effectiveness of treatment of depressive patients and show a direct impact of linguistic factors on length of hospitalization.