By definition, a pain disorder is a biopsychosocial phenomenon. Irrespective of their individual proportion, diagnostics in pain disorders must always assess biological, psychological, and social factors in order to get the full picture. Medical diagnostic procedures investigate injuries, physical diseases, or inflammation as possible causes, or contributors, to pain. Psychological diagnostic procedures assess the emotional burden of pain, emotional determinants, the appearance of dysfunctional cognitions or coping strategies, and the degree of pain-related impairment of the child’s life. Diagnostics of social factors check for dysfunctional behavior within the family system or elsewhere, and the relationship between the pain disorder and dysfunctional behavior within the family, school, or peer group. Apart from the assessment of problematic influences, it is important to identify the child’s and his/her family’s specific resources. This chapter describes the procedures necessary for a comprehensive assessment.