This study aimed to evaluate the efficacy of nourishing Yin and clearing heat therapy (NYCH therapy) based on traditional Chinese medicine (TCM) in the treatment of radiotherapy-induced oral mucositis (RTOM) in nasopharyngeal carcinomas (NPCs). A total of eight online databases were searched from inception to September 2021 for randomized controlled trials (RCTs). The control group was treated with Western medicine (WM) alone, whereas the experimental group was treated with a combined NYCH and WM therapy. A total of 30 RCTs involving 2562 participants were ultimately included. NYCH therapy combined with conventional WM delayed the onset time (days) of RTOM (MD = 10.80, < 0.001), and at that time, a higher cumulative radiotherapy dose (Gy) (MD = 5.72, < 0.001) was completed in the experimental group. The combination regimen also reduced the incidence of severe oral mucositis (Grade III-IV) (RR = 0.25, < 0.001). In addition, the treatment efficacy of the experimental group was significantly better than that of the control group (RR = 1.31, < 0.001). Compared with the patients in the control group, the experimental group had lower xerostomia scores (MD = -1.07, < 0.001) and more saliva (MD = 0.36, < 0.001). NYCH combined with WM improved the efficacy of treating RTOM in NPC. This study provides a sufficient basis for conducting further large RCTs to prove the efficacy of NYCH.