It has been reported that extraction of primary canines causes a slight mesial drift of the buccal segments, lingual positioning of the incisors, a decrease in arch length, deepening of the bite, and a slight overall crowding in the arch. The aim of this study was to investigate the effects of early mandibular primary canine extraction on permanent incisor and first molar positions, dental and alveolar arch widths, and arch length. Thirty-two patients in the early mixed dentition stage were evaluated. The treatment group (TG) included 16 patients (11 girls, five boys) who had more than 1.6 mm of crowding. Mandibular primary canines were extracted bilaterally in these patients. Another 16 patients (11 girls, five boys) who had less than 1.6 mm of crowding served as controls (CG). Mandibular dental casts and lateral cephalograms of the patients were obtained at the start (TO) and at the recall (T1) period of the trial. At the end of the one-year observation period after removal of lower primary canines, the lower incisors retruded more in the TG as compared with the CG. However, changes in arch length, arch width, and alveolar width were similar between the groups.