The Public Health Agency of Canada (PHAC) collaborated with federal and provincial partners, the U.S. CDC and U.S. health officials to investigate an outbreak of E. coli O157:H7 linked to romaine lettuce grown in the Salinas Valley, California. Four outbreak associated cases were identified in Canada. Outbreak cases resided in Alberta, Manitoba, New Brunswick and Ontario. Cases became ill in mid-October to mid-December 2019. One individual was hospitalized. There were no deaths reported. Laboratory analysis indicated that illnesses reported in Canada were genetically related to illnesses reported in the U.S.