A dealloying reaction between sputter-deposited platinum and NiCr thin films on Pyrex ® glass has been investigated. Using X-ray diffraction, 78 at.% Ni-22 at.% Cr alloy samples with platinum were studied following room temperature, 450 °C and 700 °C anneals. Although no instability was observed at room temperature, cubic Pt 3Cr and Ni 3Pt intermetallic phases emerged after annealing at 450 °C. These phases were no longer present when the anneal temperature was brought to 700 °C. There was complete dealloying of the NiCr film by the platinum, resulting in the formation of a tertiary alloy of platinum, nickel and chromium having an ordered face-centered tetragonal structure. The dealloying results are in accord with free energy calculations which are also presented. The possibility of an NiCr-glass dealloying reaction was also examined through free energy calculations and by X-ray diffraction indexing of annealed NiCr thin films deposited onto Pyrex and quartz substrates. It was found that the dealloying of NiCr by glass is self-stabilizing, with the extent of dealloying dependent on the type of glass substrate used. In this respect, an interesting anomaly between quartz and Pyrex is reported.