We aimed to assess vaccination coverage (VC) in 17-year-old French young adults (YAs) participating in one mandatory Day of Defence and Citizenship (DDC). Between June 2010 and May 2011, YAs participating in 43 randomly selected mandatory sessions of the DDC programme in Poitou-Charentes (France) were asked to provide their personal vaccination record. Tetanus, diphtheria, polio, hepatitis B, Haemophilus influenzae b, pertussis, measles, mumps and rubella vaccination status were assessed at ages 2, 6, 13 and 17 years. Of 2610 participants, 2111 (81%) supplied documents for evaluation. Of these, 1838 (87%, M:F sex ratio 0·96) were aged 17 years (9% of the global population of this age in the area). The assessment of the 17-year-olds demonstrated the following rates of complete vaccination: diphtheria-tetanus-polio 83%; measles, mumps and rubella 83%; pertussis 69%; H. influenzae b 61%; human papillomavirus 47%; and hepatitis B 40%. At age 6 years, only 46% had received two doses of the vaccine against measles. The YAs were not aware of their status but were in favour of vaccination. VC in YAs is insufficient, particularly for hepatitis B, pertussis and measles. Combined vaccines and the simplification of vaccination schedules should improve VC. Preventive messages should focus on YAs.