Isler studied thin concrete shells at the Federal Institute of Technology (ETH) in Zurich.
He is famous for his thin concrete shells. Upon graduating from the ETH in 1950 with a degree in civil engineering, Isler worked as a teaching assistant with Pierre Lardy, a professor at the ETH, from 1951 to 1953. He opened his own office in 1954 in Burgdorf, Switzerland.
His first project as a shellbuilder was a concert hall roof for the Hotel Kreuz in Langenthal which was completed between 1954 and 1955. The form of the shell was loosely inspired by the shape of a plumped-up pillow on his bed. Isler died from a stroke on June 20, 2009 at the age of 82.