Background Within the context of the recent release of the 2012 National Suicide Prevention Strategy, and as the third leading cause of death for individuals 10‐ to 24‐years‐old, suicide prevention is a national priority. A consistently reported and robust risk factor for suicide is a prior suicide attempt; however few studies have investigated the consistency of self‐reported lifetime suicide attempts. The goal of this study is to describe the prevalence and characteristics of inconsistent reporting of suicide attempt in a longitudinal cohort of participants annually assessed in 12 waves of data collected from middle school (age 12) to early adulthood (age 22). Methods Among this cohort (n = 678), we compared those who consistently, inconsistently, and never reported a suicide attempt according to demographic and clinical variables. Results Almost 90% (88.5%) of our sample inconsistently reported a lifetime suicide attempt. Consistent and inconsistent reporters of lifetime suicide attempt did not differ on demographic or clinical variables with the exception of higher rates of lifetime suicidal ideation among consistent reporters (P < .001). Significant clinical differences were evident between inconsistent reporters and nonattempters. Conclusions Some level of inconsistent reporting of suicide attempt is inevitable when schools or health care systems systematically screen for suicide risk in adolescents. Inconsistent and consistent reporters of suicide attempt differ on few demographic or clinical variables; further prospective research should investigate the reasons for inconsistent reporting as well as the validity and stability of reporting in predicting future suicidal behavior.