Chitin-graft-poly(2-methyl-2-oxazaline)/poly(vinyl chloride) (PVC) blends were characterized by means of temperature-programmed analytical pyrolysis techniques such as temperature-programmed pyrolysis-mass spectrometry (TPPy-MS), TPPy-atomic emission detection (TPPy-AED), and TPPy-gas chromatography (TPPy-GC) mainly focusing on their miscibility and sites of the intermolecular interactions. The blends degraded stepwisely in almost three stages corresponding to the degradation of respective blending polymers. However, each degradation peak temperature changed as a function of the blend composition, in particular that of the first degradation stage mostly corresponding to the dehydrochlorination stage for PVC showed a minimum temperature for the blend with the saturated composition of miscibility. During the dehydrochlorination stage for PVC, many characteristic products formed from the chitin derivative were also evolved, suggesting the intermolecular interactions between PVC and the chitin derivative. Among these, a specific hybrid product, benzoic acid reflecting the segmental interaction between PVC and the chitin derivative was observed only for the blend with the saturated composition of miscibility. The evolution peak temperatures and the amounts of the characteristic degradation products were also correlated to the miscibility of the blends. In addition, the mechanisms of the intermolecular interaction of the blends were discussed.