A thermoplastic resin composition having superior processability and impact strength has:(A) 100 parts by weight of a composition comprising 95-5 % by weight of a polyphenylene ether obtained by oxidation polymerization of at least one phenol compound represented by the following formula: ##STR1## (wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 which may be identical or different, each represents a hydrogen atom, a halogen atom, a hydrocarbon group or a substituted hydrocarbon group and at elast one of them is a hydrogen atom) and 5-95 % by weight of a thermoplastic polyester, and(B) 0.01-10 parts by weight of an amino resin obtained by modifying, with an alcohol, an addition reaction product of formaldehyde and at least one compound selected from the group consisting of melamine, guanamine and urea.