A filter for internal combustion engines, includes a rigid external casing provided with at least an inlet for a fluid to be filtered and an outlet for the fluid when filtered, and a filter cartridge located internally of the external casing, which includes a plurality of tubular filter walls arranged parallel to one another which are destined to be crossed by the fluid flowing from the inlet towards the outlet of the external casing; the external casing being conformed such as to delimit a pouch a transversal section of which, performed along a perpendicular plane to axes of the tubular filter walls, exhibits a prevalent line of development and a small width with respect to the prevalent line of development; the tubular filter walls being arranged internally of the pouch, side by side with one another, forming a single row which follows the prevalent line of development of the pouch.