Nickel has many industrial applications and is responsible for numerous cases of skin sensitization. The detection rates measured in the population were over 97% in adults and over 99% in children. The geometric means were 2.04 μg/g of creatinine in adults and 2.25 μg/g of creatinine in children, respectively. No exposure determinants were found to influence urinary nickel concentrations in either the adult or child populations. The levels measured in adults were similar to those measured in the ENNS study in 2006–2007 or in other countries except Canada. In contrast, the levels measured in children were slightly higher than those reported in the literature. These data provide an initial description of nickel concentrations in the French pediatric population, which will be useful for assessing trends over time in future biomonitoring surveys.