Disclosed are a method for positioning, a terminal, and a network-side device, which relate to the field of communications and are used to provide a means for positioning in a V2X scenario and simplify a positioning flow in the V2X scenario. In the embodiments of the present application, a first terminal determines position information of a second terminal relative to the first terminal according to received auxiliary positioning information. A means for positioning a peer device by the first terminal in the V2X scenario is provided. With this means, measuring the positions of the first terminal and the second terminal by relying on base stations is avoided, to simplify the flow of positioning the second terminal by the first terminal in the V2X scenario; and the applicability thereof is relatively high.