A tensioner, for a camshaft-camshaft chain drive with a drive chain and camshaft bearing bridge for fastening camshaft bearings to an engine block, comprises a tensioner housing with a guiding-side guide shoe, a tensioning piston slidably guided in a piston bore of the tensioner housing and provided with a tensioning-side tensioning shoe, and a fastening flange projecting laterally from the tensioner housing and having a mounting surface facing the tensioning side. A mounting plane defined by the mounting surface of the fastening flange intersects the tensioner housing at an axial distance from the guiding surface of the guide shoe at most 40% of axial transport length of the tensioner between the guiding surface of the guide shoe and the tensioning surface of the tensioning shoe. The camshaft bearing bridge has a contact surface for the fastening flange, to be in contact with the mounting surface of the fastening flange. A camshaft-camshaft chain drive for an internal combustion engine comprising such a tensioner is provided, where the camshaft bearing bridge can be attached to an engine block component.