TeliaSonera said in a statement it would begin selling the iPhone in Sweden, Norway, Denmark, Finland, Lithuania, Latvia and Estonia "later this year."
Reached by AFP, the telecom operator refused to divulge any details about the deal.
The announcement came just under two weeks after French wireless carrier Orange, which already sells the iPhone in France, said it had agreed to market the phone in more than a dozen countries in Europe, Africa, the Middle East and the Caribbean.
And at the beginning of May, British mobile phone carrier Vodafone said it would distribute the handset to customers in 10 countries by the end of the year, including South Africa and Australia.
Apple has also sealed deals with providers in Asia to distribute the iPhone, launched in June, to Singapour, India, the Philippines and is in secret talks to sell it in Japan and China.
It has said it is targeting sales of 10 million iPhones by the end of 2008.
The deal with Apple could make TeliaSonera an even more attractive target for acquisition than it already is.
France Telecom, which owns Orange, has voiced "interest" in the Swedish-Finnish group, while Russian Alfa Group and Norwegian Telenor have repeatedly been mentioned as potential buyers.