The present invention relates to an infrared sensor assembly for measuring temperature in a vehicle, including: a support bracket 3 configured to be detachably coupled with an inner surface of a garnish on one side inside the vehicle to form a base; a casing 5 configured to be detachably coupled on the support bracket 3 and form an inner installation space between the support bracket 3 and the casing 5; a main PCB 7 configured to be inserted into a PCB housing 17 so as to be interposed between the support bracket 3 and the casing 5; and an infrared sensor 9 configured to be inclinedly bound with the main PCB 7 to measure the temperature in the vehicle. By this configuration, the overall size of the infrared sensor assembly may be compacted, the infrared sensor assembly may be easily commonly used in different types of vehicles, and the infrared sensor assembly may be embedded in a garnish of an interior material, such as an A-pillar to improve an aesthetic of the interior of the vehicle.