The two drivers return to Formula One 1 for the first time since 2009, with Grosjean having won both the GP2 title and Raikkonen having raced for NASCAR and the WRC.
Grosjean has driven for Lotus Renault before, while Raikkonen joins the team for the first time. Kimi previously worked with Sauber, McLaren and Ferrari.
Grosjean commented on Kimi: "I met him last week and he's a really nice kid. I think we have more or less the same philosophy, we both want to do the best for the team, to get good results next year and I'm looking forward to working with him". The Frenchman added: "I'll be training hard until Christmas and then I'll take a few days off to relax on the beach and enjoy the sun before January.". The team that has won the world championship twice with Fernando Alonso the 2005 and 2006 finished 5th last season.