This study investigated associations between lifestyle factors and selected aspects of mental health in a group of Japanese overseas workers and their accompanying spouses who were residing in and around Düsseldorf, Germany, in February 1994. Considering four aspects of mental health (depression, mental instability, nervousness and neurosis) and six lifestyle factors (alcohol consumption, sleeping hours, cigarette smoking, physical exercise, eating breakfast and eating snacks), a cross-sectional study involving 822 volunteers (486 workers and 336 spouses) was performed using the Todai Health Index (THI) for surveying self-perceived health and a lifestyle related self-administered questionnaire. Alcohol consumption had no associations with any of the four aspects of mental health, and only very weak inverse associations were found between the other five lifestyle factors and the four aspects of mental health in the workers group. In the spouses group, physical exercise was the only lifestyle factor significantly associated with mental health.