The venture seemingly extinguishes any remaining chance of BP reviving its own deal, which lapsed in May, reported the BBC.
The agreement was signed on Tuesday in the presence of Prime Minister Vladimir Putin, a Rosneft spokesman said.
Prime Minister Putin said that it would also allow Rosneft to develop fields in the Gulf of Mexico and Texas, according to local media reports.
Under the agreement, the two firms will spend $3.2bn on deep-sea exploration in the East Prinovozemelsky region of the Kara Sea, as well as in the Russian Black Sea.
Exxon described these areas as "among the most promising and least explored offshore areas globally, with high potential for liquids and gas".
The two companies will also co-operate on the development of oil fields in Western Siberia.
Exxon spokesman Alan Jeffers told the BBC:
Analysts agreed that the joint venture would allow both sides to spread the risks of operating in the Arctic and enables Rosneft to benefit from Exxon's superior deepwater drilling expertise.
BP's own Arctic deal with Rosneft - originally agreed in January - was scuppered by a legal challenge from the Russian co-investors in BP's existing Russian joint venture, TNK-BP.