On May 2, 2018, the National Reference Center for E. coli, Shigella, and Salmonella (CNR-ESS) reported to Santé publique France a cluster of three STEC O26 strains isolated from pediatric cases of hemolytic uremic syndrome (HUS) that shared the same genomic characteristics. Epidemiological investigations began on May 3 to identify common exposures among the cases. The children’s parents were interviewed using an exploratory STEC questionnaire. All specimens from the reported pediatric HUS cases were sent to the CNR’s associated laboratory (LA-RD) for confirmation. An upstream and downstream traceability investigation was conducted by the Departmental Directorate for Population Protection (DDecPP) and the General Directorate for Food (DGAl) in collaboration with the national headquarters of the retail chains involved in the sale of the suspected products. Microbiological analyses of food and environmental samples at the producer’s facility were performed by the National Reference Laboratory for E. coli (LNR). In total, 14 children were identified in connection with this outbreak (13 confirmed cases and one probable case). These included eight girls and six boys, all under the age of 5. The cases were located in nine regions of metropolitan France, and the onset of symptoms ranged from March 3 to May 19, 2018. Thirteen children developed HUS and were hospitalized. One child died during hospitalization. In 13 cases, a strain of STEC O26 carrying the stx2, eae, and ehxA genes was isolated (one case tested negative). Phylogenetic analysis conducted by the CNR-ESS showed that the 13 strains belonged to the same genomic cluster (cgMLST HC5|65006 and SNP analysis). Consumption of Reblochon was reported in 12 of the 13 confirmed cases. In one case, consumption of Reblochon was reported within the household, but not by the case. Traceability identified that the Reblochon consumed by the cases was all produced by Chabert at the Cruseilles site (Haute-Savoie). The purchase of Chabert Reblochon could be documented (loyalty cards or receipts) for 8 out of 13 cases. For the other cases, the retailers cited by the families were indeed supplied with the implicated batches of Reblochon. Recall measures were implemented as of May 11. Additional recalls were initiated on May 14, June 1, and June 22 following new findings from the investigations. No STEC O26 strains were isolated from the suspected Reblochon cheeses. However, four STEC O26 strains were isolated from milk filters at two dairy producers supplying the Cruseilles facility. All belonged to the same cluster as that of the human cases. The results of the investigations revealed an outbreak of STEC O26 infections among young children linked to the consumption of raw-milk Reblochon produced by Chabert. This outbreak once again highlights the risk associated with the consumption of raw-milk cheeses, particularly among young children, and the need to improve public awareness of these risks.