In psittacine birds, the antemortem diagnosis of aspergillosis is usually based on the clinical signalment combined with the results of diagnostic tests such as radiography, routine hematologic and biochemical analysis, and biopsy. For several years, plasma protein electrophoresis has been used as an ancillary diagnostic technique in forming a diagnosis and treatment plan in avian species. More recently, a commercially available assay to measure galactomannan, an Aspergillus species antigen, has been described for clinical use in humans, cattle, horses, dogs, and gyr falcons. This report describes several confirmed cases of aspergillosis, with accompanying clinical data, including plasma protein electrophoresis and galactomannan assay results, in addition to results of traditional evaluations by hematology, radiography, and biopsy. In clinical cases in psittacine birds, the galactomannan assay appears useful for detecting circulating Aspergillus antibody.