Many non-human animals including monkeys, goats, pigeons, and cichlids have shown the ability to categorize objects. In this study, we examined the ability of goldfish to categorize 3D stimuli. Goldfish may use these categorization skills to aid them in identifying food sources, locating potential mates, and avoiding predators. Seven goldfish were trained to discriminate between two stimuli: a green and grey turtle and a red and yellow frog. Then they were tested with novel turtles and frogs of various colors, shapes, and sizes (e.g., green frog, yellow turtle). Five fish successfully categorized the novel stimuli (M = 68%) and two fish were unsuccessful. A second training phase with two additional stimulus pairs did not result in improved performance. It appears that the successful fish categorized the novel stimuli using shape cues, whereas the unsuccessful fish may have attended to color cues. Many of these subjects had extensive experience discriminating between the green and grey turtle and red and yellow frog presented at various aspect angles in a series of prior studies, which many have influenced which object features they used in the present study.