An increase in the rate of human infections withSalmonella enteritidis(SE) occurred between 2007 and 2010 in British Columbia (BC). During the same time period, an increase in SE from poultry-sourced isolates and increased clinical severity in poultry were also observed in BC. This article describes a multi-sectoral collaboration during a 3-year investigation, and the actions taken by public health and animal health professionals. Human cases were interviewed, clusters were investigated, and a case–control study was conducted. Environmental investigations were conducted in food service establishments (FSE). Suspect foods were tested. Laboratory data from poultry-sourced isolates were analysed. Five hundred and eighty-four human cases of SE with the same pulsed-field gel electrophoresis pattern were identified between May 2008 and August 2010. Seventy-three percentage of cases reported consumption of eggs. The odds of egg consumption were 2.4 times higher for cases than controls. Implicated FSE were found to use ungraded eggs, which had been distributed illegally. Investigation suggested that there were multiple suppliers of these eggs. Collaboration between public health and animal health professionals led to data sharing, improved understanding of SE, engagement with the poultry industry and public communication. Multi-disciplinary, multi-sectoral and multi-pronged investigations are recommended to identify the likely source of illness in large, protracted foodborne outbreaks caused by commonly consumed foods.