A thermoplastic elastomer composition superior in moldability and appearance, little in anisotropy of mechanical properties, especially, tensile strength and retaining low temperature impact strength, is obtained by previously melt-kneading an intermediate composition comprising (a) 100 parts by weight of a selectively hydrogenated block copolymer which has at least two mono-alkenyl or mono-alkenylidene aromatic hydrocarbon polymer blocks A having a number-average molecular weight of 25,000-35,000 and at least one partially or completely hydrogenated aliphatic conjugated diene hydrocarbon polymer block B having a number-average molecular weight of 100,000-150,000, (b) 50-150 parts by weight of an extender oil and (c) 0-50 parts by weight of polypropylene I, then adding, to the kneaded intermediate composition, (d) polypropylene II containing at least 35% by weight of a propylene-ethylene block copolymer having a melt flow rate of 10-30 g/10 min. and an ethylene content of 3-15% by weight in such amount that total amount of polypropylene I plus polypropylene II is 200-400 parts by weight per 100 parts by weight of block copolymer (a) and then further melt kneading the mixture. Further addition of a filler to the composition can afford a thermoplastic elastomer composition of small linear expansion coefficient with retaining the above properties.