The present invention relates to an eccentric tensioning apparatus for tensioning the traction mechanism of a traction mechanism drive. The invention is based on the object of providing solutions which provide advantages in terms of installation for the fitting of the tensioning apparatus. This object is achieved according to the invention by an eccentric tensioning apparatus for a traction mechanism drive, with: a roller device which, as such, comprises a pulley and a rolling bearing provided for the mounting of the same, a working eccentric for supporting the roller device in such a manner that the latter, by pivoting of the working eccentric, can be shifted in a radial direction with respect to the revolving axis of the rolling bearing, a torsion spring for pretensioning the working eccentric, and a fixing device for securing the working eccentric in an installation position in which the torsion spring is in a prestressed state, wherein the fixing device is designed in such a manner that it can be brought, within the scope of connection of the eccentric tensioning apparatus to a flange surface which supports it, into a release state in which the pulley, under the action of the working eccentric, is displaced radially with respect to the revolving axis of the rolling bearing towards the associated traction mechanism. This makes it advantageously possible to provide a tensioning apparatus in which the working or the operating eccentric is fixed in a final position during the installation of the traction mechanism and an activation of the tensioning apparatus is reliably ensured.