In order to optimize the bulk of a primary structure of an aircraft engine attachment pylon, and to favor the installation of the engine as close as possible to the wing element, the disclosure herein provides an aircraft assembly comprising a wing element, a turbofan engine and an engine attachment pylon, the engine comprising a rear part arranged under the wing element equipped with a wing structure, the pylon comprising a primary structure for transmitting loads from the engine to the wing structure, this primary structure comprising a pylon box, and the assembly also comprising an attachment for attaching the primary structure to the engine. According to the disclosure herein, the wing structure comprises two wing boxes that follow one another in a wingspan direction of the wing element, and the pylon box is arranged between these boxes and fixed to each of the latter.