His mother, Betty, worked the graveyard shift in a Virginia coal mine for nearly 20 years while raising seven children, including his older brother Thomas Jones.

In 2003, although he began the season as a backup to Ryan Grant, he became the starter after the fifth game when he set a single-game school record for rushing yards (262) against the University of Pittsburgh.

[5] At the start of the season, already with a bruised rib, Jones fractured his scapula bone in a win versus the Cleveland Browns early in week two and the team was forced to depend on veteran free agent acquisition Eddie George during his absence.

Jones was later healthy enough to play midway through the season and despite in a losing effort, he gained 80 yards on a stingy Baltimore Ravens defense led by Pro Bowl linebacker Ray Lewis.

A week later, on a nationally televised Thanksgiving stage against his older brother Thomas and the Chicago Bears, Julius won "player of the game" honors when he rushed for 150 yards and two touchdowns.

As a result, Jones was the second Dallas Cowboy chosen for FOX's annual "Galloping Gobbler" trophy awarded every Thanksgiving Day.

Against the Philadelphia Eagles in week 5, Julius rushed for 72 yards in the first half but suffered a high ankle sprain that bothered him the entire season and was forced to sit out for 3 games.

Bill Parcells stated he wanted to keep both running backs fresh and used a "dual-back" system with Jones as the starter and Barber as the finisher.

Jones also finally surpassed the 1,000-yard mark to become the first Cowboys back to do so since Emmitt Smith in 2001 and rushed for 112 yards in the Wildcard playoff game against the Seattle Seahawks.

Cowboys owner Jerry Jones quickly dispelled any rumors stating "I don't see that happening" and was happy with the current rotation of Dallas running backs.

During off-season workouts, with the numerous trade talks and strong public support for Barber to start, Julius chose to work out privately in Arizona away from the distractions in Dallas.

Despite openly defending Julius throughout the season, ultimately Wade Phillips decided to give Barber the start in the Divisional playoff loss to the New York Giants.

Against the San Francisco 49ers in week 2, Jones received his first start of the regular season and responded with 127 yards rushing and a touchdown in an overtime loss.

On September 14, 2009, which was also week 1 of the 2009 season, Jones rushed for 117 yards on 19 carries including a 62-yard touchdown run in a 28–0 win over the St. Louis Rams.

On October 5, he was cut after the Seahawks traded a 2011 fourth-round selection (#122-Chris Hairston) and a 2012 conditional choice (#147-Tank Carder), to the Buffalo Bills in exchange for Marshawn Lynch.

On January 8, 2011, Jones ran for two touchdowns against the Seattle Seahawks in a losing effort during the Wild Card Round of the NFL playoffs, the Saints lost 41–36.