The news confirms the 27-year-old Dutchamn's exit from Caterham, the squad with whom he spent his rookie season in 2013.
Sauber, who have signed Adrian Sutil and Esteban Gutierrez as their race drivers for this season, say that Van der Garde will be given the chance to drive in several Friday practice sessions and tests throughout the year.
“We are happy to have Giedo van der Garde on board,” said Sauber team principal Monisha Kaltenborn.
“He has four years’ experience in GP2 and he drove one year in Formula One. These are good credentials to work successfully with our team.
“Many times Giedo has shown his talent as a race driver. At the same time the team would like to support him to further develop his skills. Giedo has the right attitude to take the next step forward.”
Van der Garde said his aim for 2014 was to prove himself worthy of a race seat at Sauber in 2015.
“I consider this an important step in my career,” he said. “It is my goal to help the team with the development of the new car.
"But, of course, I am a racing driver, and I want to show the team and everybody else what I am capable of and that I deserve a race seat with the Sauber F1 Team in 2015.
“After all, my ambition remains unchanged and I am highly motivated to succeed in Formula One, especially in the long term.”
Despite losing his place at Caterham, Van der Garde paid tribute to the Leafield-based team, who have yet to name any drivers for the 2014 campaign.
“I am very thankful to Caterham that they gave me a chance to get a taste of Formula One. I enjoyed a fantastic season with the team and I have learned a lot. The experience gained will surely help me during the rest of my career,” he said.
“For now, I am really very excited to have signed a contract with the Sauber F1 Team. For every driver it is a dream to work for a well-established team such as Sauber. In recent years it has shown impressive results. I am really grateful for this opportunity and I will certainly do my upmost to succeed.”
Sauber will reveal their new car, the Ferrari-powered C33, on Monday, one day before pre-season testing begins in Jerez. The team have not said whether Van der Garde will feature at the Spanish session.