Animal hoarding is a poorly understood, maladaptive, destructive behavior whose etiology and pathology are only beginning to emerge. We compare and contrast animal hoarding to the compulsive hoarding of objects and proceed to draw upon attachment theory, the literature of personality disorder and trauma, and our own clinical experience to propose a developmental trajectory. Throughout life, there is a persistent struggle to form a functional attachment style and achieve positive social integration. For some people, particularly those affected by a dysfunctional primary attachment experience in childhood, a protective, comforting relationship with animals may form an indelible imprint. In adulthood, when human attachment has been chronically problematic, compulsive caregiving of animals can become the primary means of maintaining or building a sense of self. Improving assessment and treatment of animal hoarders requires attention to contributing psychosocial conditions, while taking into account the centrality of the animals to the hoarder's identity, self-esteem and sense of control. It is our hope that the information presented will provide a basis upon which clinicians can focus their own counseling style, assessment, and methods of treatment.