A trolley for supporting a labelling station in a labelling machine, provided with front and rear wheels for resting on the floor, comprising a longitudinal rod which is provided, at the rear end, with elements adapted to cause its rotation about its own axis and with a threaded portion with a conical tip at its front end; the rod is associated with a bush which is pivoted to the trolley with a horizontal axis and able to at least rotate with respect to it. The threaded portion is adapted to mate with a portion of female thread provided with a conical guiding portion in an accommodation bush which is fixed to a surface that protrudes from the body of the labelling machine; the surface comprises at least one ramp which is adapted to be crossed by a respective wheel provided at the front end of the trolley, and means for abutment against centering means provided on the trolley.