Serologic assays and protein electrophoresis have been used to aid diagnosis of aspergillosis in several species of captive birds, but sensitivities of these tests have not been established in psittacine birds. In 7 psittacine birds with respiratory tract aspergillosis confirmed by cytologic or histopathologic analysis, 1 bird had a positive Aspergillus antibody enzyme-linked immunosorbent assay (ELISA) titer, and 3 birds had positive Aspergillus antigen ELISA titers. In 3 birds, plasma protein electrophoretograms showed moderately to markedly increased β-globulin concentrations. Six birds had moderately to markedly decreased plasma albumin to globulin ratios. On the basis of this information, the antibody and antigen ELISA tests used in this study do not appear to be highly sensitive screening tests for aspergillosis in psittacine birds. The changes in plasma protein electrophoretograms were the more consistent findings in birds with aspergillosis, but results could also be normal in affected birds.