<p>Precipitation-strengthened medium-entropy alloys (MEAs) often display an excellent balance of strength and ductility. However, the influence of temperature on their mechanical properties and plastic deformation mechanism requires further exploration. This study examines the tensile behavior and plastic deformation mechanisms of the (CoCrNi)₉₄Ti₃Al₃ alloy at 298, 77, and 20 K using <i>in-situ</i> neutron diffraction and electron microscopy methods. The tensile property shows a clear temperature dependence. Lower temperatures result in improved mechanical performance, as indicated by an increase in yield strength, ultimate tensile strength (UTS), and elongation. Specifically, the yield strength increases from 844 to 1152 MPa at 20 K, while the UTS increases from 1306 to 1848 MPa. Similarly, elongation improves from 25.8% to 33.3% as temperature decreases. At lower temperatures, a larger number of dislocations and stacking faults form, enhancing the alloy’s strain hardening ability. Notably, dislocations exhibit wavy morphologies at 298 K, whereas planar behavior becomes predominant at 20 and 77 K. No FCC→HCP phase transformation is detected, a behavior that contrasts with the CoCrNi MEA under deformation at 20 K. Additionally, the interaction between dislocations and L1₂ nanoparticles exhibited temperature dependence, suggesting the need for future investigations. This study offers valuable insights for advancing the design of high-performance alloys suitable for cryogenic applications.</p>