Following months of discussions, the Dutchman has got the nod over Heikki Kovalainen, Vitaly Petrov, Bruno Senna and Luiz Razia to become Charles Pic's team-mate this season.
Van der Garde, who was Caterham's reserve driver last year and won races for its GP2 team, already has F1 mileage under his belt after driving in several Friday practice sessions as well as at the young driver test.
The Dutchman had also been part of the Spyker team's line-up in 2007, carrying out testing duties for the squad.
Speaking about his move in to a race seat, van der Garde said: "I know I am ready to take the step up to F1 and all the work I have done throughout my career, and particularly in the last year with this team, has brought me to my ultimate goal.
"Throughout 2012 I was able to fully integrate myself into the team, both through the FP1 sessions I ran at a number of tracks that were then new to me, and as reserve driver, fully embedded with the team throughout the season.
"Now I can continue to learn at the highest level of motorsport and show that I am ready for F1. I cannot wait to start work."
Caterham's decision to sign van der Garde and Pic is a departure from its previous mantra of securing experienced talent to help it in F1, and will have been motivated in part by financial considerations.
Team principal Cyril Abiteboul said last year that he was keen to bring on younger men now - which has been proven with his choice for 2013.
"We continue to grow as a team and we are committed to giving young talent across the motorsport industry the chance to grow with us and this is Giedo's opportunity to show he deserves his place at the very highest level of global motorsport," he said.
Van der Garde's appointment, with Razia now set to take the second seat at Marussia, means that Kovalainen, Petrov and Senna all appear to be without F1 drives for 2013
F1 tests: Super Aguri (2007), Spyker/Force India (2007/08), Renault (2009), Caterham (2012, inc Friday practice)
GP2: 2009-12 with iSport ('09), Addax ('10-11), Caterham ('12). Five wins, best championship result of fifth in 2011.
Formula Renault 3.5: 2007-08 with Victory ('07) and P1 ('08). Champion in 2008, five wins.
Formula 3 Euro Series: 2004-'06 with Signature ('04), Rosberg ('05), ASM ('06). One win, best championship result of sixth in 2006.
Pre-2003: Karting and Formula Renault Eurocup