The influence of uniaxial pressures applied along the main crystallophysical directions on the dispersion and temperature dependences of the refractive index n i of Rb2ZnCl4 crystals has been investigated. The n i value is found to be rather sensitive to uniaxial pressures, whereas uniaxial stress does not change the character of the dispersion and temperature dependences of n i. The pressure-induced changes in electronic polarizability αі, refraction R, and the parameters of UV oscillators are studied for mechanically deformed Rb2ZnCl4 crystals. The contributions of the UV and IR oscillators to the changes in n i at different temperatures, in different spectral regions, and under different mechanical stresses are estimated. The points of paraelectric–incommensurate–commensurate phase transitions (PTs) are found to undergo a significant pressure-induced shift to different temperature regions, depending on the pressure-application direction.