The purpose of this investigation was to describe the clinical and biological characteristics and evolution of invasive Fusobacterium infections in children admitted to two French paediatric tertiary care centres. Children who were admitted from 1998 to 2009 to two tertiary care centres for invasive Fusobacterium infection were included in a retrospective study. Thirty-one children with a median age of 5.7 years (interquartile range, IQR [2.3; 9.3]) were included. Nine children had an underlying condition, most commonly sickle cell disease (n = 3) or immunodeficiency (n = 3). Two children had skin effraction prior to the infection. The major sites of infection were the head and neck (n = 14) and abdomen (n = 10). Three children suffered from atypical Lemierre's syndrome. More than half of the children had a bacterial co-infection (58 %). Six children were hospitalised in an intensive care unit, and 67 % of them had a chronic underlying disease. None of the children died. Six children with negative cultures had Fusobacterium identified through 16S RNA-PCR. Fusobacterium is responsible for severe infection in children. Microbiological diagnosis might be improved by the wider use of molecular detection.