Abstract The selection of suitable polymers is pivotal in influencing the electrical performance and the thermal/electrical stabilities of organic electronics. Here, the superior properties induced by deuteration in polymer/2,8‐difluoro‐5,11‐bis(triethylsilylethynyl)anthradithiophene (diF‐TES ADT) blends are systematically investigated. By employing a combination of experimental and computational analyses, the critical factors underlying charge transport and device stabilities in deuterated polymers (d‐polymers) compared to protonated polymers are elucidated. Deuterated polymers exhibit increased mass due to the substitution of hydrogen with deuterium, reducing the zero‐point vibration energy by 1/√2. This reduction leads to enhanced energetic stabilization and the formation of stronger D─C bonds than H─C bonds. Consequently, deuterated polymers exhibit enhanced thermal properties, along with improved insulating properties, which are intrinsically linked to improved device performance. Additionally, the correlation between the electrical properties and bias stability using deuterated poly(methyl methacrylate) (d‐PMMA) and polystyrene (d‐PS) blends are analyzed. Utilizing complementary neutron & X‐ray reflectivity, and photoexcited charge‐collection spectroscopy (PECCS), phase separation and trap dynamics are delved, providing a comprehensive understanding of these relationships. These findings reveal that d‐polymers significantly enhance the electrical performance and stability of the blends, offering valuable insights for the design of advanced materials in organic electronics.