Objective The aim of this study was to evaluate the efficacy of photobiomodulation therapy (PBMT) on the mucosal healing of patients submitted to simple dental extractions after head and neck radiation therapy (HNRT). Methods Forty surgical procedures were randomly assigned into two groups: G1: dental extraction + PBMT ( n  = 19) and G2: dental extraction + sham-PBMT ( n  = 21). All patients received antibiotic therapy and the surgical alveolotomy to promote primary closure of the surgical site. Group 1 was submitted to PMBT according to the following parameters: 808 nm, 40 mW, 100 J/cm 2 , 70 s, 2.8 J/point, 14 J/session, and area of 0.028cm 2 . The primary outcome was complete mucosal lining at 14 days, and the secondary outcomes were the presence of infection, postoperative pain, and analgesics intake at 7 days. The patients were evaluated every 7 days until 28 days. Results Alveolar mucosal lining was faster in G1, and at 14 postoperative days, 94.7% patients evolved with complete alveolar mucosal lining compared to no patient from G2 ( p  < 0.001). Patients from G1 reported postoperative pain less frequently (G1 = 4, 21.1% × G2 = 14, 66.7%, p  = 0.005), and also reported lower intake of analgesic pills at D7 (21.1% × 66.7%, p  = 0.005%). PBMT had a significant positive impact on both postoperative pain (NNT = 2.192, CI95% = 1.372–5.445) and mucosal healing (NNT = 1.056, CI95% = 0.954–1.181). Conclusions This preliminary study strongly supports the use of PMBT to promote surgical alveolar mucosal lining in a shorter time and with less postoperative pain.