The present invention relates to a device 1 for attaching a windscreen-wiper blade 100 to an arm 200, comprising a connector 10 intended to be attached to the blade 100, as well as an adaptor 40 intended to be coupled, on the one hand, with the arm 200 and, on the other hand, with the connector 10 in a mobile manner, the adaptor 40 comprising at least one locking element 41, 42 capable of elastically deforming between an active position and a passive position.The invention is noteworthy in that the connector 10 comprises means for holding each locking element 41, 42 in the active position when the adaptor 40 is in the operating position, and in that for each locking element 41, 42, the connector 10 comprises an undercut enabling the elastic deformation of said locking element 41, 42 when the adaptor 40 is in the assembly position.