Third molar extraction surgery is one of the most frequently performed procedures in the areas of buccal-maxillofacial traumatology and surgery. The post-surgery evolution was evaluated based on the clinical evidence obtained so far. The objective of this study was to analyze the post-surgery clinical evolution of the masseter muscle by means of surface electromyography, to evaluate muscle activity. Four analyses were performed: one pre-surgery, to register the normal activity, and three in post-surgery: on the 7th, 14th and 21st postoperative days, in a sample of 30 patients. On the 21st day, there was near normal recovery of the electrical signal of the masseter in women, but in men this activity did not reach normal levels. Surface electromyography is a safe and reliable tool for post-surgery evolution control of masseter function.