Congestive heart failure (CHF) and atrial fibrillation (AF) are two increasingly common conditions that predispose to each other and frequently coexist. Cardiac resynchronization therapy (CRT) has emerged as an important therapeutic modality for selected patients with end-stage CHF. However, despite the high prevalence of AF in patients eligible for CRT, virtually all the randomized clinical trials that validated the benefit of resynchronization therapy excluded patients with preexisting AF. In this review, we examine the available evidence on the benefits and limitations of CRT in patients with AF and discuss recent data that narrowed the knowledge gap on this topic.