Abstract: Two-arm tensioner for an accessory drive of an internal combustion engine, including a first arm and a second arm rigidly connected to each other and rotating around a common rotation axis (A), a first pulley connected to the first arm and rotatable around its own first axis (C), a second pulley connected to the second arm and rotatable around its own second axis (E), in which the first pulley is carried by a working arm linked to the first arm and rotatable with respect to it around a third axis (B) distinct from the first axis (D), and an elastic element configured to exert on the working arm an elastic force tending to bring the first pulley closer to the second pulley, the third axis being inside the first pulley.