Background The length of hospital stay (LOHS) for elderly patients tends to be long. We aimed to identify factors related to long hospitalization periods for elderly Japanese patients with late-onset depression. Methods We retrospectively examined 133 patients with late-onset depression. Univariate and multivariate analyses were performed to confirm the relationship between each clinical feature and the duration of hospital stay. Results The mean LOHS was 83.9 +/- 55.6 days. On the basis of univariate analysis, we found that living as a housewife, death of a close relative or friend, recurrent depression, melancholic features, and treatment with electroconvulsive therapy, tricyclic or tetracyclic antidepressants or mood stabilizer were associated with a longer LOHS. Multivariate analysis showed that treatment with tricyclic or tetracyclic antidepressants, atypical antipsychotics were associated with prolonged LOHS. Conclusions These results suggest that job status, changes in household circumstances and the failure of initial treatment is responsible for the long LOHS in Japan.