Abstract: A process and a device for interlacing multifilament yarns includes forwang the yarn through an interlacing zone, to which an interlacing air jet is also conveyed through a nozzle, in a non-rectilinear trajectory which is essentially planar and symmetrical with respect to the jet axis, and under tension. The resultant of the tension forces have a line of application which ideally coincides with the jet axis and a direction opposite to that of the jet. The jet is so directed as to contact the yarn in a zone about the point of application of the resultant force. The nozzle includes an orifice located at the vertex of a convex surface directed towards the yarn trajectory, and means for guiding the yarn near the nozzle and for limiting the freedom of motion of the yarn.