Objectives: The aim of the study was to clinically evaluate the efficacy of photodynamic therapy in treatment of the reticular form of oral lichen planus (OLP). Materials and Methods: Twenty patients aged 40–76, with 40 confirmed OLP lesions in total, underwent photodynamic therapy (PDT) following the authors’ own protocol, which used 5% 5-aminolevulinic acid as a photosensitizer applied two hours prior to illumination with a diode lamp emitting light at 630 nm and 300 mW. The therapy comprised of 10 weekly illumination sessions and was clinically evaluated between its completion and the end of a 12-month follow-up. Results: While the baseline mean size of all 40 lesions was 2.74 ± 3.03 cm2, it was 2.97 ± 3.4 cm2 for the 30 lesions on the buccal mucosa and 2.02 ± 1.32 cm2 for the remaining 10 on the gingiva and tongue. On completion of the therapy, 37 sites improved, including 14 showing complete remission. From that point, the mean size reduction of 56.2% (1.2 ± 1.4 cm2) rose to 67.88% (0.88 ± 1.3 cm2) 12 months later. Conclusions: The results suggest that ALA-mediated photodynamic therapy was effective for the reticular form of OLP and may become an optional or complementary treatment.