Background: B-cell chronic lymphocytic leukemia (B-CLL) is a lymphoproliferative disorder consisting of clonal proliferation and accumulation of small, mature, CD5-positive B-lymphocytes in the blood, bone marrow, and lymphoid tissues. Among extranodal localizations, cardiac involvement is extremely rare: to our knowledge, there are no findings reported in the literature of concomitant B-CLL diagnosis in the context of atrial myxoma (so-called collision tumours) and the best strategy to treat these malignancies is unclear. Case report: We report the case of a 67-year-old woman diagnosed with B-CLL and atrial myxoma. Our patient was cardiologically symptomless and the cardiac mass was an incidental finding. The cardiac tumor appeared several years after B-CLL diagnosis. Histologic examination of the cardiac mass, removed in the suspicion of an atrial myxoma, revealed a lymphoid focus of B-CLL. The patient underwent surgery and subsequent systemic therapy for B-CLL. Conclusions: The concomitant presence of B-CLL in the context of an atrial myxoma is extremely rare. The best strategy to treat these cardiac hematologic malignancies is unclear.