Lianhua Qingke tablets, a patented traditional Chinese medicine that has validated clinical efficacy for treating cough caused by severe acute respiratory syndrome coronavirus 2 infection, lack rigorous evidence-based research evaluating their effect on long coronavirus disease (COVID) cough. A randomized, double-blind, placebo-controlled, multicenter clinical study was conducted among patients with long COVID cough from 19 hospitals and 23 community health centers in China. Patients were randomized 1:1 to receive either Lianhua Qingke tablets or placebo orally for 14 days (4 tablets, 1.84 g, 3 times a day). The primary endpoint indicator was the disappearance of cough, with the remission of cough also considered. Among 482 randomized patients, 480 (full analysis set 480; per-protocol set 470; safety set 480) were included in the primary analysis. According to the full analysis, the time until cough disappearance was significantly shorter in the trial group than in the control group, with a significant increase in the 14-day cough disappearance rate. Accordingly, the time to cough remission was significantly shorter in the trial group than in the control group. The change in the total symptom score was significantly greater in the trial group than in the control group on day 7 and 14, consistent with the results indicated by the visual analog scale (VAS) and cough evaluation test (CET) scores. No serious adverse events were recorded during the study. Lianhua Qingke tablets significantly improved the clinical symptoms of patients with long COVID cough.