The Jona rises on the eastern slope of Bachtel hill near Gibswil and Fischenthal in the Zürcher Oberland. Passing an impressive waterfall, the river flows near the municipality of Wald through a little valley eastward and changes its direction to the south by a ravine, which a viaduct of the Tösstalbahn (S26) is crossing. The Jona turns to the west, dividing the municipalities Dürnten and Rüti, passing the village of Tann and Rüti in the so-called Tannertobel. Once again, it changes its direction, flowing to the south (and slightly meandering) through Rüti and the so-called Joner Wald (forest of Rapperswil-Jona), followed by the S-Bahn Zürich lines S5 and S15. The river underneaths here Oberland Autobahn (A53 highway), now reaching the canton of St. Gallen and Rapperswil-Jona, flowing nearly in straight direction through the village of Jona (SG). Finally, it forms a small river delta near Busskirch and flows at Stampf lido in the Obersee, the upper section of the Zürichsee.