In this meta-analysis, we evaluated overall strengths of relation between beliefs about pain, health, or illness and problems in functioning (i.e., functional impairment, affective distress, pain severity) in osteoarthritis and rheumatoid arthritis samples as well as moderators of these associations. In sum, 111 samples (N = 17,365 patients) met inclusion criteria. On average, highly significant, medium effect sizes were observed for associations between beliefs and problems in functioning but heterogeneity was also inflated. Effect sizes were not affected by arthritis subtype, gender, or age. However, pain belief content emerged as a significant moderator, with larger effect sizes for studies in which personal incapacity or ineffectiveness in controlling pain was a content theme of belief indices (i.e., pain catastrophizing, helplessness, selfefficacy) compared to those examining locus of control and fear/threat/harm beliefs. Furthermore, analyses of longitudinal study subsets supported the status of pain beliefs risk factors for later problems in functioning in these groups.