Both multidimensional grief theory and multidimensional grief therapy (MGT) draw upon a rich history of the clinical and scientific study of child and adolescent (hereafter youth) bereavement. This history offers a diverse array of conceptual lenses and therapeutic tools that support a broad, integrative approach to understanding, assessing, and intervening with bereaved youth and families. As a theory derived from decades of field study and clinical practice, multidimensional grief theory is both practical and powerful in its ability to describe, explain, predict, and therapeutically address a broad range of grief reactions. As we will discuss, the theory is an outgrowth of three major streams of clinical research, theory, and practice: attachment theory, existential philosophy, and disaster mental health (Layne, 2021b).