We report development of the first all‐polyimide system (cladding/core/cladding) suitable for fabrication of electro‐optic waveguide devices on silicon substrates. The cladding layers are spun from a low optical loss, commercially available polyimide that is suitable for multilayer stacks. The electro‐optic material consists of this same polyimide as host to a commercially available guest chromophore and is based upon our prior work on thermoplastic polyimides [J. F. Valley, J. W. Wu, S. Ermer, M. Stiller, E. S. Binkley, J. T. Kenney, G. F. Lipscomb, and R. Lytel, Appl. Phys. Lett. 60, 160 (1992)]. We present the materials and process development methodology with the results for this polymer system and demonstrate it by fabrication of an all‐polyimide Mach–Zehnder modulator operating at 830 nm.