The spotted lanternfly adult is about 2.5 cm (1 inch) in length. The fore wings are greyish-brown with black spots, with the wing tips having a darker, brick-and-mortar pattern. The hind wings are mainly red with black spots, followed by a white band and a black tip. When the spotted lanternfly is at rest, a hint of the red color can be observed through the forewings, but the color is especially noticeable when it is in flight. The body is mainly black, but the abdomen appears to be mostly yellow with black bands going down its length. Adults can be found as early as July, and they will remain active until the onset of winter. In late fall, the adults will mate, and the female will begin egg-laying. Spotted lanternfly females prefer to lay their eggs on the tree-of-heaven, but will lay their eggs on any flat vertical surface, including other trees, stones, vehicles, outdoor furniture, and many others. The eggs are laid in groups of approximately 30-50, and then coated with a waxy gray film. When this film has dried, it can look similar to a splash of mud, which can make them difficult to notice. The eggs will hatch in the spring, usually in late April or early May. The nymphs are small and are black with white spots when they first hatch. As the nymphs mature, they start to show red coloring, especially around their head, abdomen, and wing pads. One habit that has been observed in the nymphs is a tendency to crawl up the tree in the morning, and then back down the tree in the evening. As the nymphs often do this in large groups, it can be very noticeable.

Spotted lanternfly causes damage to plants in two different ways. The nymphs and adults feed on plants using their piercing mouthparts to suck fluids from the stems or leaves. This has been shown to cause stunted growth, localized damage, reduced yields, and, in extreme cases, even death of the plant. Additionally, as the spotted lanternfly feeds, it excretes a sugary substance called honeydew. This honeydew, in addition to being attractive to ants, wasps, and other insects, is readily colonized by sooty mold, which can cause parts of the plants to become blackened, reducing photosynthesis and affecting the quality of the plants.

It should also be noted that the spotted lanternfly has been found on other crops, such as corn, soybeans, and alfalfa, although there has been no observed feeding on these plants.