The C18 struggled throughout the 1999 season with a large number of retirements. On just 12 occasions did a C18 cross the finish line of a Grand Prix, with Diniz chalking up 12 retirements in 16 races, failing to finish a Grand Prix until Canada in round 6. Alesi meanwhile fared slightly better with 8 retirements. Alesi scored the first points of the season in Round 3 at San Marino with a 6th place finish. Diniz would score the team's next 3 points with 6th place finishes at the Canadian, British and Austrian Grand Prix. Alesi added the team's final point at the final Grand Prix of the season in Japan.

At the end of the season, Diniz and Alesi finished 14th and 15th in the Drivers' Championship respectively, while Sauber finished eighth in the Constructors' Championship, their five points being their lowest tally since their entry into F1 in 1993.