The invention relates to a device for protecting the inside of vehicles. Said device comprises: at least one U-shaped arch (1), the shape of which is complementary to the inner shape of the walls (11), roof (12) and/or floor (14) of the inner compartment (13) of a motor vehicle (10), provided with elements (2) for securing to the body, that detachably and dismountably secure the arch (1) to the inside of the inner compartment; and a IV laminar protection cover (3) provided with connecting means (5) that connect to the arches (1) by means of the cooperation of said strips (5) with at least one arch-fixing element (4). The invention provides a device that is easy to install and protects the inside of vehicles that carry loads or aggressive elements that dirty and/or damage the loading area of the inside of the body and/or the upholstery thereof.