The purpose of this in vitro study was to evaluate the ability of lateral compaction of gutta-percha and of five thermoplasticized gutta-percha filling techniques to obturate simulated lateral canals. Sixty extracted single-rooted human teeth were instrumented at the working length to a #35 file before creating three simulated lateral canals on the mesial and distal surfaces of the root, one in each third, using a #15 engine reamer. After enlarging root canals to a #45 file, the teeth were randomly divided into six equal groups of 10 and obturated according to the following techniques: lateral compaction of gutta-percha (group A), hybrid technique (group B), Ultrafil (group C), Obtura II (group D), System B + Obtura II (group E), and Thermafil (group F). AH26 was used as the sealer. A greater number of simulated lateral canals were obturated when Ultrafil, Thermafil, and System B + Obtura II were used, in comparison with canals obturated with the hybrid technique, Obtura II, or lateral compaction of gutta-percha. This difference was statistically significant (p < 0.05). No statistically significant differences were found between results obtained in the obturation of simulated lateral canals in the different thirds of the root (p > 0.05).