"Romain is a great talent and we are pleased that he is continuing with us for a second season," said team principal Eric Boullier in a statement.
"With the continuity of two exceptional drivers like Romain and Kimi we are well placed to build on our strong 2012 with even better results in the year ahead."
Lotus finished the 2012 season as the fourth-placed team overall, with Grosjean taking three podium placings and ending the championship eighth overall. Raikkonen, the 2007 champion with Ferrari, was third. (Reporting by Alan Baldwin, editing by Ed Osmond)