The dating of microinclusions of organic material in a sample from the upper part of the Pleistocene syngenetic ice wedge, exposed in an outcrop of the Vilyui yedoma, located in the north of Yakutia, near the village of Kysyl-Syr (coordinates: 63°53′19″ N, 122°46′09″ E, height above sea level 100 m), was performed using accelerator mass spectrometry (AMS). The dated fragment of the ice wedge was formed about 22.5–22.3 cal. ka BP (18.46 ka radiocarbon years BP). Based on the isotopic data, the mean January air temperature of the Late Pleistocene was calculated from 22 to 23 cal. ka BP for the Vilyui section. It is shown that the mean January air paleotemperature during this period in the basin of the Vilyui River varied from –44 to –42°C.