Background: Previous studies have shown that relational coordination is positively associated with the delivery of hospital care, acute care, emergency care, trauma care, and nursing home care. The effect of relational coordination in primary care settings, such as disease-management programs, remains unknown. Purpose: This study examined relational coordination between general practitioners and other professionals in disease-management programs and assessed the impact of relational coordination on the delivery of chronic illness care. Methodology: Professionals (n = 188; response rate = 57%) in 19 disease-management programs located throughout the Netherlands completed surveys that assessed relational coordination and chronic care delivery. We used a cross-sectional study design. Findings: Our study demonstrated that the delivery of chronic illness care was positively related to relational coordination. We found positive relationships with community linkages (r = .210, p qqqlt; .01), self-management support (r = .217, p qqqlt; .01), decision support (r = .190, p qqqlt; .01), delivery system design (r = .278, p qqqlt; .001), and clinical information systems (r = .193, p qqqlt; .01). Organization of the health delivery system was not significantly related to relational coordination. The regression analyses showed that even after controlling for all background variables, relational coordination still significantly affected chronic care delivery (β = .212, p ≤ .01). As expected, our findings showed a lower degree of relational coordination among general practitioners than between general practitioners and other core disease-management team members: practice nurses (M = 2.69 vs. 3.73; p qqqlt; .001), dieticians (M = 2.69 vs. 3.07; p qqqlt; .01), physical therapists (M = 2.69 vs. 3.06; p qqqlt; .01), medical specialists (M = 2.69 vs. 3.16; p qqqlt; .01), and nurse practitioners (M = 2.69 vs. 3.19; p qqqlt; .001). Practice Implications: The enhancement of relational coordination among core disease-management professionals with different disciplines is expected to improve chronic illness care delivery.