To provide a reinforcing polyester textured yarn that has both high strength and high adhesiveness and has sufficient durability.

The method for producing a polyester textured yarn includes: surface-treating a polyester filament in which the amount of terminal carboxyl groups in molecules existing in the filament is 15 equivalents/ton or more with an agent which reacts with a carboxyl group and stretch-breaking the surface-treated polyester filament. It is preferable that the amount of terminal carboxyl groups on a filament surface of the polyester filament is 10 equivalents/ton or less before stretch-breaking, that the polyester filament contains ethylene-2,6-naphthalate as a main repeating unit, and that the surface treatment is an epoxy treatment. It is also preferable that the polyester textured yarns have an average fiber length of 20 to 150 cm after stretch-breaking.