Pharmacological antiarrhythmic therapy such as beta-blockers in patients with frequent premature ventricular contractions (PVCs) and concomitant bradycardia is challenging. A traditional Chinese medicine, Shensong Yangxin (SSYX), has been effective in treatment of frequent PVCs and sinus bradycardia (SB) in separate patient cohorts. This double-blind, placebo-controlled, multicentre, randomized clinical trial investigates the acute efficacy of SSYX in reducing PVCs burden in patients with concomitant SB. Patients with symptomatic, frequent PVCs, and SB, defined as mean heart rate (MHR) of 45 to 59 beats per min (bpm), were recruited at 33 medical centres in mainland China and randomly assigned by computer to either SSYX or matching placebo for eight weeks. Patients, investigators, and trial personnel were masked to treatment allocation. Primary endpoints were changes in PVCs burden and MHR as assessed by 24-hour Holter monitoring relative to baseline. Secondary efficacy endpoints were subjective symptom score, ECG, and biochemical parameters. Analysis was based on intention-to-treat principles. 333 patients were randomized, of which 166 received SSYX and 167 placebo. Baseline characteristics did not differ. SSYX reduced PVCs burden by 68.2% (p < 0.001) and increased MHR by 10.9% (p < 0.001) compared to 32.2% and 4.7%, respectively, in the placebo group. SSYX group experienced greater symptomatic improvement (p < 0.001). No differences in reported adverse events were seen (20 versus 23). SSYX is an effective antiarrhythmic therapy for symptomatic, frequent PVCs uniquely suited patients with concomitant SB. Clinical trial number was NCT01750775.