To improve the management of depression and the prevention of suicide, we investigated associations between lifestyle, working environment, depressive symptoms and suicidal ideation. Variables measured included job stressors, working hours, overtime work, smoking status, alcohol consumption, sleep, exercise, meals, and family factors. Original items were used to measure working on holidays, number of confidants, use of stress reduction techniques, and suicidal ideation. A total of 4,118 employees (2,834 men, 1,284 women) in eleven cities and districts across Japan were analyzed. On stepwise multivariate logistic regression analysis, variables associated with depressive symptoms were exposure to high job stress, problem drinking, a feeling of insufficient sleep, absence of confidants, and no use of stress reduction techniques in both sexes. Further, problem drinking and absence of confidants were associated with suicidal ideation in both sexes. The prevalence of workers who had no confidants and who did not use stress reduction techniques was unexpectedly high. Given their clear association with depressive symptoms, greater attention to these factors should improve measures aimed at the prevention of suicide.