Provided are a thermoplastic polymer composition having good mold processability, flexibility, rubber elasticity, scratch resistance, abrasion resistance, transparency, ease of coating, and mechanical properties when formed into a sheet or film, a sheet or film produced using the thermoplastic polymer composition, and a multi-layered film. The thermoplastic polymer composition includes (I) a block copolymer having a number average molecular weight of 30,000 to 200,000, or a hydrogenated product thereof, which has a polymer block (A) mainly composed of α-methylstyrene units and a polymer block (B) mainly composed of conjugated diene compound units or isobutylene units, (II) an acryl-based polymer, and (III) a softening agent at a ratio satisfying the formulae (1) and (2) as described in claim 1, and has a sea-island structure in which the components (II) are dispersed in the form of particles in a continuous phase including the component (I), in which the average dispersed particle diameter of the dispersed particles of the components (II) is 200 nm or less, and 35% by mass or more of the dispersed particles have dispersed particle diameters of less than 60 nm.