The present study aimed to survey systems in Japanese companies for supporting workers returning to work from sickness absence due to mental illness. A questionnaire survey was mailed to 3,545 companies. Support systems for return to work, sick leave, and multiple sick-listed (MSL) workers were examined. A total of 161 companies responded to the survey (response rate: 4.5%). About 80% of the companies expressed difficulty in dealing with workers with mental health problems. About half of all companies reported having reset period and financial compensation systems, as well as gradual resumption and trial attendance systems. Most large companies tended to have reset period and trial attendance systems. No association was found between company size and MSL rates. The most frequent diagnosis among workers was depression, and the mean number of sick leave days was 275.3. Although there might have been a selection bias due to the low response rate, the results of this study are expected to be useful for companies when formulating employment systems.