Separation Anxiety Disorder (SAD) is the most commonly diagnosed and impairing childhood anxiety disorder, accounting for approximately 50% of the referrals for mental health treatment of anxiety disorders. While considered a normative phenomenon in early childhood, SAD has the potential to negatively impact a child's social and emotional functioning when it leads to avoidance of certain places, activities and experiences that are necessary for healthy development. Amongst those with severe symptoms, SAD may result in school refusal and a disruption in educational attainment. This paper provides a comprehensive review of the current literature on SAD etiology, assessment strategies, and empirically supported treatment approaches. New and innovative approaches to the treatment of SAD that also employ empirically supported techniques are highlighted. In addition, future directions and challenges in the assessment and treatment of SAD are addressed.