Pacemakers are more commonly recommended than theophylline for sick sinus syndrome (SSS) treatment. The positive effects of cilostazol on bradyarrhythmias also have been reported. However, no comparison of cilostazol and theophylline has been previously reported found. We retrospectively enrolled SSS patients, who refused a pacemaker implantation. Theophylline or cilostazol was administered, and the heart rate (HR) was evaluated in 4-8 weeks using a digital sphygmomanometer and the electrocardiogram (ECG). A 200-400 mg of theophylline or 100-200 mg of cilostazol were administered per day in 50 and 30 patients, respectively. The baseline HR was 54.8 \pm 13.5 beats per minute (bpm) on using sphygmomanometry and 51.9 \pm 11.8 bpm using the ECG. In the theophylline group, the HR increased by 12.0 \pm 16.3 bpm by sphygmomanometry (P 0.001) and 8.4 \pm 12.0 bpm by the ECG (P 0.001). In the cilostazol group, the HR increased by 16.8 \pm 13.9 bpm by sphygmomanometry (P 0.001) and 12.4 \pm 13.4 bpm using the ECG (P 0.001). In 15 of the 50 theophylline patients, the medication was switched to cilostazol. The HR increased from 61.4 \pm 13.8 bpm to 64.0 \pm 12.6 bpm (P = 0.338). Symptoms such as dyspnea, chest discomfort, dizziness, and syncope significantly improved after the administration of the medications. There were no significant differences in the improvement in the symptoms except for dizziness between the two agents. Cilostazol was as effective as theophylline for increasing the HR in SSS patients.