Introduction: Our objective was to elucidate the differences in treatment outcomes caused by the different mechanics of temporary anchorage devices (TADs) and Class III elastics in patients with Class III malocclusions. Methods: Records of 23 patients with Angle Class III malocclusion were selected retrospectively. All had been treated with nonextraction comprehensive orthodontic treatment; 11 were treated with TADs and 12 with Class III elastics. Pretreatment and posttreatment lateral cephalograms were used for evaluation of the treatment outcomes. A paired t test and a Student t test were used for statistical analysis. Results: In both groups, proper overjet and Class I molar relationships were achieved, and the occlusal plane was rotated counterclockwise. In the elastics group, distal tipping of the mandibular molars, extrusion of the mandibular incisors and maxillary molars, clockwise rotation of the mandibular plane angle, and increased ANB angle were observed. In the TADs group, distal tipping and intrusion of the mandibular molars, bodily movement of the mandibular incisors, and reduced mandibular plane angle were observed. Conclusions: In nonextraction treatment for Class III malocclusions, the mandibular plane angle was increased in the elastics group, whereas it was decreased in TADs group. Thus, we suggest that Class III elastics are preferred for low-angle, short-face patients, whereas TADs are preferred for high-angle, long-face patients.