A device and a method twist single cables about a twisting axis to form a cable bundle along an extension axis. The device includes mutually spaced single rotating units for separately holding cable ends at one end of the single cables; a twisting unit for holding and twisting cable ends at the other end of the single cables; and a guiding apparatus, to which is fastened a guiding mandrel for separating the single cables, at least in some regions, during a twisting process by the twisting unit, in a region in which there is a transition from an untwisted region to a twisted region. The guiding mandrel includes a thickened portion on a side opposite its fastening to the guiding apparatus, the thickened portion having larger dimensions in a direction transverse to the running direction of the guiding mandrel than in most of the guiding mandrel.