Coatis [including Nasua nasua, the ring-tailed coati], are medium-sized mammals widely distributed in the Americas. They are social animals, whose normal diet includes insects, fruits, and small vertebrates, and rarely prey on larger sized animals. There are, to our knowledge, no reports in the medical literature of attacks on humans. This report describes a coati attack on 2 children in their home. The children sustained deep scratches and bites. The animal may have injured the humans in a defensive strike, but motivation for attack was uncertain. Coati attacks may occur in places where there is interaction between these mammals and humans.