One of the limiting factors in understanding immune responses in marsupials is the scarcity of marsupial specific immunological reagents. This paper describes the characterisation of an antiserum raised against a recombinant protein of the constant region of the heavy chain of IgA (C(alpha)) of the common brushtail possum (Trichosurus vulpecula). The availability of a marsupial specific anti-IgA provides a useful tool for the characterisation of mucosal immune responses in possums. Anti-C(alpha) specifically detects IgA in possum serum and secretions using ELISAs, immuno-dot blots and Western blots without any cross-reactivity to IgG. The possum anti-C(alpha) cross-reacts with IgA of koala (Phascolarctos cinereus), tammar wallaby (Macropus eugenii) and eastern grey kangaroo (Macropus giganteus), demonstrating the potential for use in other marsupials.