The zebra mussel is named for the striped pattern usually found on its shell, which is triangular or D-shaped. The shell has a flattened underside and a very sharp edge. The species displays many variations in shell pattern, colour and shape. Although typically small, some specimens can reach up to five centimetres in length.

Using stringlike projections called “byssal threads,” the zebra mussel is able to attach itself to various surfaces underwater. The threads are so strong that removing the mussel can be very difficult.