The former Germany star claims the Blaugrana's performance in the Champions League last term has demonstrated that they are past their best
The Blaugrana won three Ligas, two Champions League titles and two Copa del Rey trophies under then-coach Pep Guardiola who is now at Bayern.
Kahn believes Guardiola will be able to keep the treble winners at the top in football, despite many experts predicting Barca to bounce back under Gerardo Martino and the signing of Neymar.
"I believe that Barcelona's best days are over,” Kahn told TV Movie.
"There are no dominant teams in Europe which a German side must fear.
"The formative success of Bayern calls for a change and new ideas. I think the team will find a solution to this task with their many intelligent players."
Barca face Sevilla at Camp Nou this weekend before turning their focus towards their Champions League opener with Ajax on September 18.