The Chinese mountain cat (Felis bieti) is among the most elusive and endangered felid species worldwide and is endemic to the eastern edge of the Tibetan Plateau, China. Currently, the cat is assessed as Vulnerable by the IUCN Red List based on its ‘likely small population’, ‘high likelihood of fragmentation’, and “probably declining” trend. Specifically, two human activities were identified by the previous studies as the major threats that this unique lineage is faced with, as the large-scale pika poisoning program and illegal hunting prevailing in the area. However, during our monitoring of a breeding family discovered in the Sanjiangyuan Region, two cats of the family were found dead and were most likely killed by free-ranging dogs. Moreover, following genetic analysis indicated that both cats were genetically contaminated by local domestic cats. Consequently, based on the examination of the carcasses, associate genetic analysis, and survey on free-ranging dogs, in this study we identified two so far overlooked threats for the Chinese mountain cats, as the killing by free-ranging dogs and genetic contamination from domestic cats. These threats mark the tricky balance among humans, domestic animals and wildlife in both historical and recently burgeoning human activities, which requires further investigation, research and conservation efforts.