The purpose of the present study was to explore the relationship between suicidal behavior and socio-demographic and clinical factors, including insight into illness, in patients with schizophrenia spectrum disorders. We evaluated 104 inpatients using the Self-Appraisal of Illness Questionnaire (SAIQ) for insight assessment, several Beck-related symptoms rating scales, and the Positive and Negative Syndrome Scale (PANSS) for psychopathology. These patients were also evaluated for suicidal behavior and risk using the critical items of the Scale for Suicide Ideation (SSI) and lifetime suicide attempts. Patients with suicidal behavior generally had greater insight into illness than those who were non-suicidal. After controlling for depressive symptoms, the association of insight into illness with current suicidal ideation remained significant, whereas the association between insight and lifetime suicide attempts was no longer significant. As predicted, the regression analyses revealed that those with greater suicide risk had significantly higher levels of depressive symptoms and hopelessness and more lifetime suicide attempts. Moreover, greater insight into illness appeared to have a close, independent connection to suicidal behavior. Our findings suggest that depression, hopelessness, and greater insight into illness are major risk factors for suicide in patients with schizophrenia. It is plausible that depression mediates the relationship between greater insight into illness and suicidal behavior. Aggressive improvement of insight without the risk of deteriorating depressive symptoms may be warranted to reduce the risk of suicide.