An outbreak of giardiasis occurred among staff of a job training center after a meeting at a restaurant. Twenty-seven (75%) of 36 attendees became ill compared with 1 (3%) of 31 staff members not attending (relative risk, 23.3; 95% confidence interval, 3.4-161.4). Because most attendees ate all items on a fixed menu, no individual food item could be conclusively associated with illness. Circumstantial evidence suggests, however, that ice contaminated by a food handler may have been the vehicle. The restaurant had multiple sanitary violations, and 2 employees, 1 with asymptomatic giardiasis and the other with a Giardia-infected, diapered child, served ice to the attendees. This outbreak demonstrates the potential for restaurant-based giardiasis outbreaks.