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Pt-containing NiAl (more simply referred as Pt aluminide) coatings have been widely used in jet engines either as stand-alone oxidation and hot-corrosion resistant coatings or as bond coats in thermal barrier coating systems for life extension and for increased temperature capabilities of the airfoils. To enable computational design and life prediction of these coatings (especially for simulating coating – substrate interactions), phase diagram and diffusivity information of the Ni-Al-Cr-Pt system (including Ni-Al-Cr, Ni-Al-Pt, Ni-Cr-Pt, and Al-Cr-Pt) are essential. Among these ternaries, only Ni-Al-Cr has been well assessed. The remaining three ternaries were studied in the present research using a Ni-Cr-Pt diffusion multiple together with a series of aluminization treatments and electron probe microanalysis to extract phase equilibria and interdiffusion coefficients. Ternary isotherms have been established for Ni-Cr-Pt at 1200 °C, Ni-Pt-Al at 1150 °C, and Cr-Pt-Al at 1010 °C, which either improve upon and expand on existing isotherms or introduce an entirely new phase diagram (Ni-Cr-Pt). Interdiffusion coefficients were extracted using the Hall, Wagner, and Sauer-Freise methods for Ni-Cr, Ni-Pt, Cr-Pt, Ni-Al, Pt-Al, and Ni-Pt-Al systems. The data presented in this thesis will be used to develop both thermodynamic and mobility databases to be applied to the design, processing development, and life prediction of Pt-containing airfoil coatings.