Background/Objectives: Point-of-care (PoC) manufactured fresh chimeric antigen receptor (CAR)-T cells are typically formulated in hypothermic preservation formulations (HPFs) and stored under hypothermic conditions (2–8 °C) until administered to the patient. However, in current HPFs the shelf life of fresh CAR-T cells is short (~24–36 h) due to limited CAR-T cell stability, which poses significant time constraints on manufacturing procedures and logistics. The objective of this study was to improve the stability and extend the shelf life of fresh clinical-grade CAR-T cell drug products (DPs). Methods: A novel HPF was developed by supplementing a base HPF with the novel excipient SUL-138, which stabilizes mitochondria during hypothermic storage and subsequent rewarming, alone or in combination with endogenous mitochondrial substrates. This panel of HPFs was first screened for their stability-improving characteristics in the model cell line Jurkat cells. Subsequently, HPFs were assessed for their stability-improving characteristics of clinical-grade CD19 CAR-T cell DPs. Critical quality attributes, including CAR-T cell viability, T-cell differentiation state, exhaustion markers, and functional potency were evaluated in a good manufacturing practice (GMP)-compliant stability study up to 72 h. Results: For Jurkat cells, HPFs supplemented with SUL-138 and a combination of glucose, glutamine, and succinate demonstrated the greatest stability improvement at 2–8 °C, improving cell viability from ~1% to >85% after 72 h. For CAR-T cells, supplementation of HPFs with SUL-138 alone demonstrated the greatest improvement, resulting in a CAR-T cell viability from ~40% to >85% after 72 h of storage at 2–8 °C, while no additional benefits from mitochondrial substrates were observed. The novel HPF did not significantly impact CAR-T cell potency test results, T cell subset distribution, or exhaustion markers compared to control. Conclusions: A novel clinical-grade HPF that significantly improved fresh CAR-T cell stability during hypothermic storage was developed. This novel HPF can aid in the establishment of GMP-compliant and PoC CAR-T cell manufacturing platforms.