The swelling and phase transition behavior upon increasing temperature of a doubly thermoresponsive diblock copolymer thin film in steps above the characteristic cloud points (CPs) of the blocks is studied. An upper critical solution temperature (UCST)-type zwitterionic poly-(sulfobetaine), poly(N,N-dimethyl-N-(3-methacrylamidopropyl)-ammoniopropane sulfonate) (PSPP, CP UCST = 31.5 °C), is combined with a lower critical solution temperature (LCST)-type nonionic poly(N-isopropyl-/ methacrylamide) (PNIPMAM, CP LCST = 49.5 °C) block. Using time-offlight neutron reflectivity (ToF-NR), we observe the swelling in D 2 O vapor at a constant temperature of 20 °C, followed by two subsequent temperature jumps, from 20 to 40 °C (above CP UCST ) and from 40 to 60 °C (above CP LCST ). The observed response of the diblock copolymer films deviates from the aqueous solution behavior, which is mainly attributed to the increased polymer concentration. Temperature-induced changes in the thin-film nanostructure are investigated with ToF grazing-incidence small-angle neutron scattering (GISANS). Alterations in the chain conformation and hydrogen bonding are probed by Fourier transform infrared (FTIR) spectroscopy. The ionic SO 3 − groups (in the PSPP block) and the nonionic hydrophilic amide groups (in both blocks) are found to affect the mechanisms of D 2 O uptake and release significantly.