The BMSB is a large shield bug, a similar size to several native species. It has generally brown and marbled coloration. The key features to distinguish the adult from other native shield bugs are its rectangular-shaped head and rows of pale dots across the body behind the head. It also produces a distinctive smell resembling coriander plants and, when it is present in high numbers, this may be considered unpleasant and disturbing. The juvenile stages (nymphs) are easier to recognise because, unlike any native shield bugs, they have spines on the sides of the body.

Adults have been intercepted in imported goods and luggage and a few individuals found free out of doors in England but so far other life stages (nymphs or eggs, confirming breeding) have not been found.
In 2022, a female, found in South East England, laid eggs after capture, though these were unviable. This suggests that the shieldbug may become established, especially with warmer summers which favour the insect.

The BMSB has a very wide host-plant range, feeding on more than 100 plant species, including important crops such as apples and brassicas alongside many ornamental and woody plants. It is a very mobile insect, which likes to move and feed on the sap of different plant parts including leaves, flowers, fruit and seedpods. Its feeding activity can be particularly troublesome, with low densities of the insect causing deformed flowers and fruit.