The Sea Princess cruise line says 53 people had symptoms of norovuris during the cruise.
The ship is back in San Francisco undergoing sanitization and disinfection with the help of the Center for Disease Control and Prevention.
Passengers say the outbreak had little impact on the overall trip.
"The food service was, perhaps, slowed down a bit," said passenger Christine Gregg. "Tourists like me couldn't reach in and pick up a roll, the roll had to be handed to us with tongs and all of the employees kept things cleaner a nicer."
Norovirus is a common sickness that is easily transmitted from person-to-person. Symptoms usually include severe stomach pain, vomiting and diarrhea that usually lasts between one and three days.