Bmi regional is stepping up the service from Monday to Thursday with single flights on Sundays and Fridays. The changes from today came after the service began with a single daily flight in October last year to the Norwegian capital.
The airline said it means business travellers can spend a day in either city and the move is also expected to boost inbound leisure traffic to the north-east.
The oil and gas industry and Scandinavia are key markets.
Cathal O'Connell, chief executive of bmi regional, said it demonstrated its commitment to the business community. He said: "Aberdeen is now firmly established as an important hub in our European scheduled network with one-third of our 400 staff and seven of our 18-strong fleet of Embraer jets based here.
"The support of businesses at both ends of the route has exceeded our expectations and we are now responding to feedback from our customers by delivering additional frequency. When we launched our Aberdeen to Oslo service last year we committed to increasing the frequency if demand required it and we are now delivering on that promise."