Reports indicate that Andrographolide inhibits viral replication and reduces COVID-19 symptoms. This study aimed to determine Andrographolide's additional effect and safety in mild COVID-19 patients treated with favipiravir. A multicenter, open-labeled, randomized controlled trial was conducted from October 2021 to February 2022. The patients were randomized to receive a combination of Andrographolide and favipiravir or favipiravir monotherapy. The primary outcome was the occurrence rate of severe pneumonia. The secondary outcomes were symptom improvement, inflammatory biomarkers, and adverse events on days 7 and 14. 82 mild COVID-19 patients were enrolled; 43 and 39 patients received either combination therapy or favipiravir alone. Baseline characteristics were comparable. None developed severe pneumonia, requiring a mechanical ventilator. The Andrographolide group had a significant reduction of cough compared to the controlled group; 13 (30.2%) vs. 22 (56.4%), p = 0.017 on day 7 and 4 (9.3%) vs. 7 (17.9%), p = 0.025 on day 14. Moreover, the Andrographolide group had significantly lower levels of inflammatory markers on day 7, CRP (5.8 vs. 18.4 mg/L; p = 0.019) and IL-6 (2.0 vs. 21.8 pg/mL; p = 0.001) but not on day 14. Regarding safety outcomes, the Andrographolide group had significantly higher AST levels on day 7 (40.3 vs. 32.2 U/L; p = 0.030) and both AST and ALT levels on day 14 (55.3 vs. 32.0; p = 0.014 and 63.8 vs. 40.0; p = 0.022, respectively). In mild COVID-19 patients, the combination of Andrographolide and favipiravir did not demonstrate additional benefits over favipiravir alone in preventing severe pneumonia. However, Andrographolide significantly reduced cough symptoms, especially during the first week. Furthermore, despite mild transaminitis, patients treated with Andrographolide showed improvements in inflammatory markers.