Despite consistent links between interpersonal problems and worry, mechanisms explaining this relationship remain unknown. The Contrast Avoidance Model (CAM; Newman & Llera, 2011) posits that individuals at risk for chronic worry and generalized anxiety disorder (GAD) fear sudden negative mood shifts, using worry to perpetuate negative moods and avoid these negative emotional contrasts. We propose interpersonal (IP) contrast avoidance (e.g., acting friendly to prevent others from causing mood shifts) as a novel explanation for interpersonal dysfunction in worriers. This study investigated IP contrast avoidance and worry in two samples. A nonclinical sample ranging in GAD symptoms (Study 1; N = 92) reported IP problems at baseline then IP contrast avoidance and worry over eight weeks (637 diaries). As expected, baseline IP problems prospectively predicted worry indirectly through chronic IP contrast avoidance. Affiliative, submissive, cold, and total IP contrast avoidance strategies predicted same-week and lagged next-week worry increases; affiliative, submissive, and total strategies also predicted maintenance of worry over eight weeks in growth models. Lastly, Study 2 showed the relevance of IP contrast avoidance strategies in a treatment-seeking clinical sample (N = 40), correlating with interpersonal problems and worry. Overall, results provide proof-of-concept for extending the CAM to the interpersonal domain.