The aim of this study was to determine whether conventional hemostasis (CH) or the harmonic scalpel (HS) results in shorter operative times for thyroidectomy and to evaluate the incidence of postoperative complications with each approach. In this study, 85 consecutive patients undergone open thyroidectomy were randomized into two groups: group CH (conventional hemostasis with classic technique of tying and knots, resorbable ligature, bipolar diathermy) and group HS (harmonic scalpel). Demographics, pathological characteristics, thyroid size, operative time, blood loss, and complications using the Student's t-test and χ (2)-test. The two groups were similar regarding age and sex. There were no intraoperative complications. There was no difference between the two techniques regarding the amount of blood loss for different procedures. No significant differences were found between the two groups concerning mean thyroid weight and mean hospital stay (2.2 days in HS vs. 3.7 in CH; P > 0.05). The mean operative time was significantly shorter in the HS group (47.2 min vs. 79.2 min; P < 0.001). Two (4.7 %) transient recurrent laryngeal nerve palsies were observed in the CH group and no one (0 %) in the HS group. No patient developed permanent palsy. Postoperative transient hypocalcemia occurred more frequently in the CH group (21/43, 48 % vs. 7/42, 16 %). In patients undergoing thyroidectomy, HS is a reliable and safe tool. Comparing with CH techniques, its use reduces operative times, postoperative pain, drainage volume, and transient hypocalcemia.