West Brom had appeared to be zeroing in on the former Huddersfield Town manager, but Wagner will not be the new boss at the Hawthorns.
It is claimed that the Baggies wanted to be sure that Wagner had the appetite for a promotion battle in the Championship.
However, it became clear that Wagner preferred to stay closer to his family in Germany, making Young Boys his choice.
Young Boys eased to the Swiss Super League title last season and will play Champions League football next term.
Wagner will now look to plot the defence of Young Boys’ title, along with mounting a push to make an impact in Europe’s top cup competition.
West Brom’s search for a new manager will go on as they look to instantly return to the Premier League.
The Baggies had been keen to keep Sam Allardyce at the helm at the Hawthorns, but he chose to depart following their relegation.