Energy intake under-reporting (UR) is a concern in nutritional epidemiological studies, as it may distort the relationships between dietary habits and health. Although UR is known to be associated with certain characteristics, few studies have investigated them in France. Therefore, the goal of the present study was to assess the prevalence and characteristics of UR in French adults. UR was defined according to Goldberg's classification. A sample of 1567 adults was drawn from the nationally representative French dietary survey (Individuelle Nationale des Consommations Alimentaires 2 2006–7). Food intake (7 d record), dietary habits, socio-economic status, region of residence, sedentary behaviour and weight perception variables were assessed. Multivariate logistic regression was used to investigate the associations between UR and a number of covariates. The overall prevalence of UR was 22·5 %, similar in men and women. In both sexes, UR was positively associated with overweight and protein intake and inversely associated with age. In women, UR was associated with eating lunch in the office, poor perception of diet quality and sedentary behaviour and was inversely associated with educational level, residence in the Paris region, cereal product intake and eating lunch in a friend's or family member's home. In men, UR was positively associated with a history of slimming and inversely associated with dairy product intake and eating lunch at a staff canteen. In conclusion, UR is prevalent in French adults and is associated with several different characteristics. It is important to take account of UR when investigating diet–disease associations in adults.