The brown widow spider, Latrodectus geometricus C. L. KOCH, 1841, is recorded from Japan for the first time. Some females with egg sacs and numerous spiderlings were collected in the winter season in an urban park adjoining the container wharf at the port of Yokohama. According to the information received from colleagues by personal communication, spiders of this species were also found at the ports of Tokyo, Nagoya, Osaka and Okinawa, and some other dominant trade ports in Japan.