Introduction: while some of scholars believe that combining adult and adolescent suicidal behavior findings can result in misleading conclusions, some of researchers have stated that suicidal behavior may be a different phenomenon in adolescents than in adults. Hence, in the present study, the clinical profile of suicidal behavior among adult and child & adolescent psychiatric inpatients, has been compared with each other, to assess their resemblances or variances, in a non-western, local patient population. Methods: five acute academic wards, which have been specified for admission of first episode adult psychiatric patients, and five acute non-academic wards, which have been specified for admission of recurrent episode adult psychiatric patients, had been selected for current study. In addition, child & adolescent section of Razi psychiatric hospital was the field of appraisal concerning its specific age-group. All inpatients with suicidal behavior (successful suicide and attempted suicide, in total), during the last five years (2013-2018), had been included in the present investigation. Besides, clinical diagnosis was based on Diagnostic and Statistical Manual of Mental Disorders, 5th edition. Intra-group and between-group analyses had been performed by ‘comparison of proportions’. Statistical significance as well, had been defined as p value ≤0.05. Results: As said by results, during a sixty months period, sixty-three suicidal behaviors among adult patients, including one successful suicide and sixty-two suicide attempts, and fourteen suicide attempts among child & adolescent patients, without any successful one, had been recorded by the security board of the hospital. While among adults and child & adolescent patients no significant gender-based difference was evident, with respect to suicidal conduct, among adults, the most frequent mental illness was bipolar I disorder, which was significantly more prevalent in comparison with other mental disorders. The other disorders included schizophrenia, major depressive disorder, personality disorders (borderline & antisocial), substance abuse disorders, and adjustment disorder. Among child & adolescent subjects, the most frequent mental illness was, once more, bipolar I disorder, followed by conduct disorder, and substance abuse disorder. Moreover, no significant difference was evident between the first admission and recurrent admission cases in adults or child & adolescents. While self-mutilation, self poisoning and hanging were the preferred methods of suicide among both groups, self-mutilation was significantly more prevalent than the other ways. Conclusion: While the annual incidence of suicidal behavior in inpatient adults and child & adolescents was comparable, bipolar disorder was the most frequent serious mental illness among suicidal subjects of both groups. Moreover, self-mutilation was the preferred method of suicide in adult and child & adolescent psychiatric inpatients.