Dwight Bowling appeared Wednesday in U.S. District Court in Greenville.
Court records show the 56-year-old pleaded guilty to two counts of taking a minor across state lines, from Mississippi to Alabama, for sex.
Bowling pleaded guilty to one count of obstruction for trying to get someone else to lie to investigators.
A sentencing date was not immediately set.
Bowling coached 28 years at Smithville High School in Monroe County, Miss., before retiring and taking a similar job at Sulligent High in Sulligent Ala.
He was the coach for the Alabama school when he was arrested last September in Mississippi, on his way home from a football game.