This article describes the synthesis and characterization of several methyl nadimides end-capped resins based on tris (3-aminophenyl) phosphine oxide. These resins were prepared by reacting methyl-5-norbornene 2,3-dicarboxylic anhydride (methyl nadic anhydride) (MNA), pyromellitic dianhydride (PMDA)/3,3’,4,4’-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6F), and tris (3-aminophenyl) phosphine oxide (TAP) in glacial acetic acid/acetone. Structural characterization of the resins was done by elemental analysis, IR, and H-1-NMR. Thermal characterization of uncured resins using DSC and TGA techniques revealed an exothermic transition accompanied by a weight loss in the temperature range of 200-350-degrees-C. Residual weight at 800-degrees-C in nitrogen was found to be 47-55%. Isothermal curing of the resins was done at 340-degrees-C for 1 h in an air atmosphere. The cured resins were stable up to 400 +/- 20-degrees-C.