Provided is a thermoplastic polyester resin composition comprising 100 parts by weight of (A) a non-liquid crystal thermoplastic polyester resin, 45 to 150 parts by weight of (B) a thermoplastic resin that is different from the non-liquid crystal thermoplastic polyester resin and has a dielectric loss tangent of not more than 0.005 when measured at a frequency of 5.8 GHz by the cavity resonance perturbation method, 2 to 20 parts by weight of (C) a compatibilizer having at least one reactive functional group selected from epoxy, acid anhydride, oxazoline, isocyanate, and carbodiimide groups, and 0.2 to 5 parts by weight of (D) at least one compound selected from tertiary amines, amidine compounds, organic phosphines and salts thereof, imidazoles, and boron compounds, wherein the ratio of the sum of the thermoplastic resin (B) and the compatibilizer (C) is in the range of 50 to 150 parts by weight and the weight ratio (B)/(C) of the thermoplastic resin (B) to the compatibilizer (C) is in the range of 8 to 50. The thermoplastic polyester resin composition can be molded into an article with low dielectric properties, excellent mechanical properties, and high bondability to metals.