A newly formulated chemical additive from a group of amines has been tested and applied to in-situ heavy oil thermal recovery. Switchable-hydrophilicity chemical additives were successfully synthesized from N,N-dimethylcyclohexylamine in the form of homogeneous and hydrophilic solution. Fundamentally, tertiary amines comprise functional groups of hydrophilic and hydrophobic components. These unique features enable this chemical additive to wet both water and heavy oil, yielding potential interfacial tension (IFT) improvement. Furthermore, the reversible chemical reaction of this chemical additive yields both positive and negative ions. An ion pair formed due to the adsorption of cations—[C8H17NH+]—on the surface of heavy oil, whereas the anions—[HCO3−]—promoted solid-phase surface charge modification, therefore, resulting in the repulsive forces between heavy oil and the rock surface—substantially improving water-wetness and restoring an irreversible wettability alteration due to the phase change phenomenon during steam injection. In this research, two types of heavy oil acquired from a field in western Alberta encompassing the viscosity of 5,616 and 46,140 cp at 25°C was utilized in each experiment. All experiments were performed and measured at high-pressure, high-temperature (HPHT) steam conditions up to 200 psi and 200°C. We perceived that favorable IFT reduction was achieved, and irreversible wettability could be restored after combining switchable-hydrophilicity tertiary amines (SHTA) with steam as a result of the solid-phase surface charge modification to be more negatively charged. Phase distribution/residual oil in the porous media developed after steam injection was able to be favorably recovered, indicating that capillary forces could be reduced. Consequently, more than 80% of the residual oil could be recuperated post-SHTA injection, presenting favorable oil recovery performance. In addition to this promising evidence, SHTA could be potentially recovered by switching its reversible chemical reaction to be in hydrophobic form, hence, promoting this chemical additive to be both reusable and more economically effective. Comprehensive studies and analyses on interfacial properties, phase distribution in porous media, and recovery performance exhibit essential points of view in further evaluating the potential of SHTA for tertiary recovery improvement. Valuable substantiations and findings provided by our research present useful information and recommendations for fields with steam injection applications.