Both carriers are set to combine cheap flights to Copenhagen, Demark from Oslo in Norway and Stockholm in Sweden from September 15th.
However, they will continue to market, price and sell tickets for their flights independently.
Neither carrier has mentioned the possibility of a full merger or acquisition.
Reports suggest the two airlines are waiting to see how the new deal will compare with the performance of competing carrier SAS.
Commenting on the decision last week, Reza Taleghani, CEO of Sterling, and Bjorn Kjos, CEO of Norwegian, emphasised the efficiency and flexibility that the new agreement will bring for both operators.
The deal will also provide passengers with more choice over which timetabled routes they may take between destinations.