Provided is a thermoplastic resin composition, in particular, an aliphatic polyester resin composition comprising a plasticizer which is soft, exhibits high transparency, is reduced in bleeding out and exhibits high resistance to the extraction by a paraffinic solvent; and a sheet, a film or a molded article formed from the thermoplastic resin composition. An aliphatic polyester resin composition, characterized in that it comprises 100 parts by mass of an aliphatic polyester and, as a plasticizer, 1.0 to 100 parts by mass of a specific ester compound which is an ester formed from a trivalent polyhydric alcohol and an acyl group derived from a carboxylic acid having 2 to 18 carbon atoms and has an average acylation degree of 50 to 90%.