High-entropy alloys (HEAs) consist of four or more principal elements and exhibit a high-entropy effect thermodynamically, sluggish diffusion effect kinetically, a lattice distortion effect crystallographically, and a cocktail effect in usage, which results in excellent mechanical properties and corrosion resistance. Transformation-induced plasticity (TRIP) HEAs undergo a martensitic transformation during deformation, which delays crack initiation and increases the work-hardening rate of the metal, addressing the plasticity-strength dilemma. This makes them highly promising for research and application. Cast HEAs often suffer from severe segregation and coarse grain defects, leading to poor mechanical properties in the formed samples. Additive manufacturing, characterized by rapid solidification in the local molten pool, produces HEAs with uniform compositions and fine grains, resulting in mechanical properties that are far superior to those of cast parts. This paper discusses the research progress on the microstructure, mechanical properties, microstructural evolution, and corrosion resistance of TRIP HEAs formed by additive manufacturing and anticipates future research directions.