The invention relates to a tensioning device of a belt and chain drive with a tensioning lever (2) which is provided with a rotatable tension roller (6) mounted rotatably by means of a rocker pivot (3) constructed as a plain bearing on a base housing (4), and radially at a distance from the axis of rotation (5) of the rocker pivot (3); with a pretensioned torsion spring (11), which is constructedas a helical spring (12, 12'), disposed coaxially with the rocker pivot (3) and connected at the spring ends (13, 14) thereof at the housing side to the base housing (4), and at the lever side to thetensioning lever (2); and with a brakeshoe (16, 16' 29) which is disposed at one spring end (13, 14) and which can be pressed by said spring end against a component which can rotate about the axis ofrotation (5) of the rocker pivot (3) relative to the spring end (13, 14). In order to achieve good heat dissipation of the friction damping device and uniform stress on the rocker pivot (3), the brakeshoe (16, 16') is constructed in such a manner and is disposed at the lever-side spring end (13) of the helical spring (12, 12') in such a manner that said brakeshoe (16, 16') is clamped peripherallybetween the spring end (13) and a radially directed stop surface (23, 23') of a catch attached to the tensioning lever (22, 22') and, by means of a contacting force (FS_R) resulting from the two peripheral tangential forces (FF_T, FF_T') from the helical spring (12, 12') and on the helical spring (12, 12'), can be pressed with an outer cylindrical friction surface (17) largely radially against a cylindrical inner wall (19) of the base housing (4).