Illness beliefs affect how individuals and families deal with illness. A valid and reliable instrument has not yet been developed to measure "illness beliefs" in family nursing research and clinical practice. This article describes the purpose, reliability, validity, and the potential clinical and research applications of a new instrument, the Iceland-Family Illness Beliefs Questionnaire (ICE-FIBQ). The ICE-FIBQ is a short, self-report measure of an individual's beliefs about illness. Drawing from an advanced nursing practice model called the Illness Beliefs Model, the instrument was developed to measure illness beliefs about (a) cause of illness, that is, etiology; (b) control of illness on family and control of family on illness; (c) effect of illness on the individual and family; (d) illness suffering; and (e) support received from health care professionals during illness. The instrument was tested on 139 family caregivers of adolescents/youth with an illness or a disorder. Exploratory factor analysis reduced the original questionnaire from eight to seven items with a one-factor solution (Cronbach's a = .780). Confirmatory factor analysis supported the one-factor solution (Cronbach's a = .789). Further research is needed to determine concurrent validity with other illness belief/illness perception scales and if the instrument is sensitive to capture change in illness beliefs following family nursing intervention.