Minnesota Department of Health (MDH) and Washington County Public Health (WCPHE) staff investigated an outbreak of norovirus among individuals who at a restaurant located in Woodbury, Minnesota on January 6, 2012. A total of 75 restaurant patrons identified from credit card receipts were interviewed. Ten patrons met the case definition. The median incubation was 24.5 hours (range, 20.5 to 48 hours). The median duration of illness was 39 hours (range, 6 to 95 hours). No one sought medical care. No one died. Two case stool specimens were positive for norovirus Gii.4 Sydney with identical region D nucleic acid sequences. By univariate analysis, consuming buffalo chicken pizza (2 of 8 cases vs. 0 of 55 controls; odds ratio [OR], undefined; p=0.01) and consuming an entrée that contained fresh lettuce (5 of 10 cases vs. 10 of 52 controls; OR, 4.2; 95% confidence interval 1.02 to 17.4; p=0.05) were statistically associated with illness. WCPHE and MDH maintained a daily presence at the restaurant from January 12 through January 18 to provide management and staff education, conduct employee interviews, and monitor food handling and preparation practices. Employees were interviewed regarding recent illness history and work duties at the restaurant. A total of 102 active employees were identified at the restaurant. Interviews were conducted with 100 of those employees. Of those, 15 had been ill since December 26 with symptoms of vomiting and diarrhea. Investigators concluded that the outbreak associated with eating lettuce and buffalo chicken pizza. Substantial numbers of ill employees were reported. Improper glove use, improper handwashing, and poor management practices contributed to the outbreak.