In this study, the authors examined the role of parental beliefs about the causes of child problems in predicting later mental health service use in a large, diverse population of at-risk youths. Study hypotheses were that parental beliefs consistent with biopsychosocial causes would be associated with later mental health service use; sociological, spiritual, or nature disharmony etiologies would be negatively associated with service use; and beliefs would partially mediate the relationship between race/ethnicity and service use. Of the 5 biopsychosocial beliefs, 2 were positively related to later mental health service use. Unexpectedly, of the 6 parental beliefs related to sociological, spiritual, or nature disharmony etiologies, only 1 was negatively associated with later service use patterns. Parental endorsement of etiologies relating to physical causes, relational issues, trauma, and prejudice was found to partially mediate the relationship between race/ethnicity and service use for Asian/Pacific Islander American and Latino youths.