The miscibility and complexation behavior of poly(cyanomethyl methacrylate) (PCYMMA) and poly(2-cyanoethyl methacrylate) (PCYEMA) with various tertiary amide polymers was studied. PCYMMA and PCYEMA form interpolymer complexes with poly(N-methyl-N-vinylacetamide) (PMVAc) or poly(N-vinyl-2-pyrrolidone) (PVP) in tetrahydrofuran (THF) solutions. PCYMMA also forms complexes with poly(N,N-dimethylacrylamide) (PDMA) in THF solutions. However, PCYEMA does not form complexes with PDMA in THF solutions, but the THF-cast blends are miscible over the entire composition range. Both PCYMMA and PCYEMA do not form complexes with poly(2-ethyl-2-oxazoline) (PEOx) in THF solutions and are only miscible with PEOx when the blend contains greater than 60 wt % PCYMMA or 80 wt % PCYEMA. On the other hand, both PCYMMA and PCYEMA do not form complexes with PMVAc, PVP, or PDMA in N,N-dimethylformamide (DMF) solutions. The compositions of the complexes consist of simple mole ratios of the component polymers, and the glass-transition temperatures of the complexes are higher than those of the DMF-cast blends of similar compositions. Fourier-transform infrared spectroscopy provides further evidence on the miscibility behavior through changes in the amide carbonyl absorption bands of each tertiary amide polymer in the blends as well as in the cyano absorption band of PCYEMA.