Absenteeism from school is a serious public health issue for mental health professionals, physicians, and educators. The prevalence of unexcused absences from school exceeds that of major childhood behavior disorders and is a key risk factor for violence, injury, substance use, psychiatric disorders, and economic deprivation. This article involves a contemporary research review on absenteeism prevalence, comorbid physical and psychiatric conditions, classification, contextual risk factors, cross-cultural variables, assessment, intervention, and outcome. Contextual risk factors include homelessness and poverty, teenage pregnancy, school violence and victimization, school climate and connectedness, parental involvement, and family variables, among others. A description of intervention includes medical, clinical, and systemic interventions. Medical professionals, community- and school-based mental health professionals, and educators are encouraged to fully understand the parameters of school absenteeism to develop better, consensual policies regarding definition, classification, assessment, and intervention of youths with problematic school absenteeism.