Suicide has a great impact on the individual whose life is lost and the bereaved family members. The risk of a suicide reattempt is particularly high during the first 12 months after a suicide attempt. In this cohort study, risk factors for a suicide reattempt were explored among 291 patients at suicide risk. Clinical and demographic data were collected from a Japanese primary care hospital. Past psychiatric history and multiple diagnoses were associated with suicide reattempts in both genders. Drug overdose, past psychiatric history, and the summer season were linked to suicide reattempts among males. Past psychiatric history and multiple diagnoses were linked to suicide reattempts among females. Appropriate assessment of past psychiatric history, season and method of suicide attempt, gender, and diagnosis may play a role in preventing suicide.