An integrated thermal management system may include a battery line connected to a high-voltage battery, having a first radiator, and having cooling water flowing by a first pump; an internal heating line connected to an internal air-conditioning heating core, having a cooling water heater therein, having cooling water flowing by a second pump, and having a first valve at a downstream side of the heating core; a first battery heating line formed to be diverged from the internal heating line at a downstream side of the internal air-conditioning heating core and connected to the battery line at an upstream side of the high-voltage battery; a second battery heating line diverged heating line formed to be diverged from the battery line at a downstream side of the high-voltage battery and connected to the internal heating line; and a controller operating the first pump and the second pump.