Thermally triggerable polymer films that degrade at modest temperatures (≈85 °C) are created from a blend of cyclic polyphthalaldehyde (cPPA) and a polymeric thermoacid generator, poly(vinyl tert‐butyl carbonate sulfone) (PVtBCS). PVtBCS depolymerizes when heated, generating acid which initiates the depolymerization of cPPA into volatile byproducts. The mass loss onset for 2 wt% PVtBCS/cPPA is 22 °C lower than the onset for neat cPPA alone in dynamic thermogravimetric analysis experiments. Increased concentrations of PVtBCS increase the rate of depolymerization of cPPA. Raman spectroscopy reveals that the monomer, o‐phthalaldehyde, is the main depolymerization product of the acid‐catalyzed depolymerization of cPPA. The PVtBCS/cPPA blend is a promising material for the design and manufacture of transient electronic packaging and polymers. A thermally triggered transient material is presented that depolymerizes to volatile products, leaving less than 2 wt% of residuals. Poly(vinyl t‐butyl carbonate sulfone) is shown to be an effective thermoacid generator and thermal depolymerization trigger for poly(phthalaldehyde) films, lowering its thermal depolymerization temperature and increasing its depolymerization rate. The reported polymer blend enables rapidly vanishing polymer films at moderate temperatures.