The nuclear power plant in canton Aargau, Beznau, is the oldest operating plant in the world and it will now run until 2033.
The energy company, Axpo, is to spend CHF 350m on renovations to keep it going.
It first went online in 1969 – with a second reactor in 1971.
The company says the decision has been made after extensive reviews and stresses safety is its top priority.
This is the first time a specific shutdown date has been given.