The pair found the treasure Wednesday in a handbag left on the seat of a train running between Oslo and a small town in southeastern Norway.
"When I opened the bag, the first thing I saw were these wads and wads of bills," one of the teens, identified as 16-year-old Bendik, told local daily Vestby Avis.
"My first thought was to call the police," he said.
After looking in the bag more closely, the good Samaritans found the passport of its owner, a man in his 70s who was expected to pick up his money from the police on Thursday.
Police said they did not suspect any foul play behind the man's huge quantity of cash, and said they did not know if the two teenagers had been rewarded for their honesty.