We have identified a scarcely known river otter population from the Upper Rio Conchos basin, northern Mexico, finding a well-established population of the Nearctic otter Lontra canadensis. A pioneer study of these otters at Rio San Pedro, a tributary of the Rio Conchos, described them as Neotropical otters, Lontra longicaudis; at that time, no specimens or photographs of these otters were available from the locality. Therefore, its taxonomic status remained unclear for various decades. Rio Conchos is one of the major tributaries of Rio Grande (Rio Bravo in Mexico) and its headwaters are located high in the Sierra Madre Occidental. A juvenile otter fur obtained from Rio San Pedro was compared to two furs of Neotropical otters from Oaxaca and Sonora, with the aim to compare the structure of primary hairs (PH) and secondary hairs (SH) in order to know their specific status. Camera traps were set-up at Rio San Pedro in Chihuahua and in Arroyo Bamochi (occupied by L. longicaudis) in Sonora in 2015 to compare individuals, population structure and occupation in both places. Two other places were surveyed to confirm the presence of river otters: Rio Conchos and Rio Santa Isabel. Based on hair characteristics (primary and secondary hairs from the juvenile) and photographic evidence from camera-traps, we confirm that otters from Rio San Pedro, belong to the Nearctic otter, Lontra canadensis. And presumably in other localities visited in the Concho’s river basin that also has presence of otters, such as Rio Santa Isabel and Rio Conchos. The population structure from Arroyo Bamochi and Rio San Pedro were similar in both areas, but the density of otters is higher at Arroyo Bamochi than at Rio San Pedro, even though there is no significant difference between the two sites. Specimens of river otters from Rio Grande basin have been identified as L. canadensis lataxina, Cuvier, 1823. The former distribution area of this species ranges from inland US across the Rio Grande basin in the Rocky Mountains, the Rio Pecos, further East, flowing south and southeast into the Gulf of Mexico. The finding reported here represents a major area occupied by this species, and a significant conservation issue for their protection in Mexico, as well as an indicator of the healthy conservation status of the upper Rio Conchos