Abstract: The present invention provides a Modular Integrated Car Safety Seat (MICSS 100) that comprises a base assembly that includes a seat and a backrest assembly rotatably connected to the base assembly. The backrest assembly features an adjustable headrest with an adjustment mechanism and actuator, as well as safety belts. The MICSS further includes a seat height adjustment mechanism for the seat and an inclination adjustment mechanism for adjusting the backrest assembly into at least two detachable locked positions for use as a car safety seat or as a regular vehicle seat cushion. The base assembly is configured for rigid attachment to a vehicle's chassis, while the adjustment mechanisms are enclosed within the base and backrest assemblies so that in the stored position, all components are contained within the external boundaries of the MICSS, allowing for interchangeable installation with a vehicle's seat cushion or a portion thereof.