The invention is to provide a thermoplastic resin composition rich in heat resistance, oil resistance, and thermal aging resistance and excellent in tensile elongation characteristics, by adding a specific partially hydrogenated block copolymer to a styrene resin and/or poly(phenylene ether) resin and an olefin resin. The invention relates to a thermoplastic resin composition which comprises (A) from 95 to 5% by weight of styrene resin and/or poly(phenylene ether) resin, (B) from 5 to 95% by weight of olefin resin, and (C) a partially hydrogenated block copolymer in an amount of from 2 to 30 parts by weight per 100 parts by weight of the sum of ingredients (A) and (B), wherein (C) is a partially hydrogenated block copolymer obtained from a block copolymer which has at least one polymer block X mainly comprising a vinylaromatic compound and at least one polymer block Y mainly comprising a conjugated diene compound and has a combined vinylaromatic compound content of from 30 to 80% by weight and in which the vinyl bond amount in the polymer block Y mainly comprising a conjugated diene compound is from 20% by weight to less than 65% by weight, by hydrogenating from 35% to less than 70% of the double bonds derived from the conjugated diene compounds.