Abstract Background: In this experimental protocol, we evaluated the immediate and delayed repair of the buccal branch of the facial nerve (BBFN) with heterologous fibrin biopolymer (HFB) as a coaptation medium and the use of photobiomodulation (PBM), performing functional and histomorphometric analysis of the BBFN and perioral muscles. Methods: Twenty-eight rats were divided into eight groups using the BBFN bilaterally (the left nerve was used for PBM), namely: G1 - control group, right BBFN (without injury); G2 - control group, left BBFN (without injury + PBM); G3 - Denervated right BBFN (neurotmesis); G4 - Denervated left BBFN (neurotmesis + PBM); G5 - Immediate repair of right BBFN (neurotmesis + HFB); G6 - Immediate repair of left BBFN (neurotmesis + HFB + PBM); G7 - Delayed repair of right BBFN (neurotmesis + HFB); G8 - Delayed repair of left BBFN (neurotmesis + HFB + PBM). Delayed repair occurred after two weeks of denervation. All animals were sacrificed after six weeks postoperatively. Results: In the parameters of the BBFN, we observed inferior results in the groups with delayed repair, in relation to the groups with immediate repair, with a significant difference (p < 0.05) in the diameter of the nerve fiber, the axon, and the thickness of the myelin sheath of the group with immediate repair with PBM compared to the other experimental groups. In measuring the muscle fiber area, groups G7 (826.4 ± 69.90) and G8 (836.7 ± 96.44) were similar to G5 (882.8 ± 70.51). In the functional analysis, the G7 (4.10 ± 0.07) and G8 (4.12 ± 0.08) groups presented normal parameters. Conclusion: We demonstrated that delayed repair of BBFN is possible with HFB, but with worse results compared to immediate repair, and that PBM has a positive influence on nerve regeneration results in immediate repair. Background protocol (BBFN (HFB PBM, , (PBM) muscles Methods Twentyeight Twenty PBM) namely G without injury) neurotmesis (neurotmesis) HFB) PBM. . denervation postoperatively Results p 0.05 005 0 05 axon area 826.4 8264 826 4 (826. 69.90 6990 69 90 836.7 8367 836 7 (836. 96.44 9644 96 44 882.8 8828 882 8 (882. 70.51. 7051 70.51 70 51 70.51) 4.10 410 10 (4.1 0.07 007 07 4.12 412 12 0.08 008 08 Conclusion (PBM 0.0 00 826. 82 (826 69.9 699 6 9 836. 83 (836 96.4 964 882. 88 (882 705 70.5 5 4.1 41 1 (4. 0. (82 69. (83 96. (88 70. 4. (4 (8 (