This invention relates to IL-9 muteins that inhibit the activity of wild-type IL-9, multimers and Fc-fusion constructs of IL-9 proteins, and an efficient method to purify IL-9 proteins produced by eukaryotic cells. Related formulations, dosages and methods of administration thereof for therapeutic purposes are also provided. More particularly, these IL-9 muteins, compositions, and methods provide a treatment option for individuals afflicted with conditions where inhibiting IL-9 mediated immune responses would be beneficial, such as allergy, asthma, chronic obstructive pulmonary disease (emphysema and chronic bronchitis), pulmonary and gastro-intestinal mucus hyperplasia, inflammation, immunological disorders, leukemia, and lymphoma.