Potamotrygon motoro, also known as the Marble motoro, is a potamodromous freshwater ray native to the basins of the Amazon River. Marble motoros were introduced to South Korea in the 2000s, and, because they are easy to raise, were sold as aquarium fish. The aim of this report is to illustrate a new case involving envenomation by a Marble motoro. A 35-year-old commercial aquarium assistant came to the hospital after being pricked by a Marble motoro. The clinical picture in this case showed acute local pain with minimal systemic manifestations. This patient recovered after receiving symptomatic treatment and wound care. This case of envenomation accentuates the potential for injury among people coming in contact with a venomous Marble motoro.