An adjustable camshaft sprocket assembly includes a hub and a sprocket body secured to the hub. A stud-receiving opening is defined in one of the hub flange and the sprocket body, and a tool-receiving opening is defined in the other of the hub flange and the sprocket body. The tool-receiving opening is aligned with the stud-receiving opening and is adapted to receive a body portion of an adjustment tool, and the stud-receiving opening is adapted to receive an eccentric stud of the adjustment tool. Either the stud-receiving opening or the tool-receiving opening is elongated. Rotation of the adjustment tool when its body is located in the tool-receiving opening and its eccentric stud is located in the stud-receiving opening causes relative angular movement between the hub and the sprocket body. One or more fasteners are used to immovably secure the sprocket body to the hub after adjustment. A tool includes cylindrical base, a driving head, and an eccentric stud. The stud comprises a spring pin press-fit into a bore.