As of the 2000 census, there were 455,466 people living in Jefferson Parish.
In the parish the population was spread out with 25.30% under the age of 18, 9.10% from 18 to 24, 30.20% from 25 to 44, 23.40% from 45 to 64, and 11.90% who were 65 years of age or older.