The aim of the study was to evaluate Photobiomodulation (PBM) as an analgesic alternative following endodontic instrumentation. The patient received single-session endodontic treatment on both upper right molars. After standard treatment, PBM was applied to tooth 17, while tooth 16 underwent a simulation. At the end of the procedures, the patient received a Visual Analog Scale to record pain at 4, 8, and 12 hours post-treatment, along with analgesics for use only in case of maximum pain. After 24 hours, a reassessment was conducted. There was a reduction of over 50% in spontaneous pain parameters at all time points, reaching zero at 4 hours. There was a reduction of over 50% in vertical percussion and about 29% in horizontal percussion. Palatal palpation showed an increase of 36%. There was no need for analgesic use. It is concluded that PBM may be an analgesic alternative for post-endodontic instrumentation spontaneous pain.