Zoledronic acid (ZA) is one of the important bisphosphonates which is widely used in bone metastatic cancer and osteoporotic patients. In a few studies, it has been reported that treatment with bisphosphonates was associated with an increased risk of atrial fibrillation. We aimed to evaluate the arrhythmias that developed during and immediately after infusion of the ZA. Fifty-two bone metastatic patients were included in the study group. All patients had 24-h Holter monitorization during the first dose ZA infusion day. All of the patients had 4-h basal cardiac rhythm records before ZA infusion and about 19 h after infusion. A short survey including demographic data and past medical history has been completed. None of patients had clinically important arrhythmias before ZA infusion. We divided arrhythmias into two groups as supraventricular and ventricular. We evaluated arrhythmias in pre-infusion, during infusion, and post-infusion periods. ZA was administered 4 mg intravenously (IV) in 15 min. Thirty-three of patients (63.5 %) were male and 19 (36.5 %) patients were female. Mean age of the patients was 53.9 +/- 11.8 years. Most frequent cancers were breast (25 %) and lung cancer (15.3 %). Twelve (23 %) patients had history of mediastinal radiotherapy. In basal records, we detected that twenty-four (46 %) of patients had supraventricular premature complexes (SVPC) or ventricular premature complexes (VPC). Fifteen (28.8 %) of patients had SVPC and fourteen (26.9 %) had VPC during infusion period. After infusion period, 48 (92.3 %) of patients had SVPC and 41 (78.8 %) had VPC. Only 3 patients had no arrhythmia after infusion. Three patients had sinus arrhythmia and two had Mobitz type 2 atrioventricular blocks after infusion. One patient, who had no history of comorbidities and had SVPC in the basal records, developed atrial fibrillation that was refractory to medical cardioversion after 10 days of seventh dose of ZA infusion. In this study, we found that both SVPC and VPC increased in cancer patients treated with ZA. Furthermore, ZA may induce clinically important arrhythmias.