He first played for Australia’s Davis Cup team in 1999, and competed at Sydney in the 2000 Summer Olympics.Hewitt beat Pete Sampras in the finals of the 2001 U. Open to claim his first Grand Slam singles championship.

His younger sister is Jaslyn Hewitt, a former tennis coach and bodybuilder and his brother-in-law (Jaslyn's husband) is Rob Shehadie.

Lleyton also played Australian Football until the age of 13, when he decided to pursue a tennis career.

The next year he won the Wimbledon men’s singles title with a straight-sets win over David Nalbandian. Men’s Clay Court Championship in Houston in April of 2009, bagging his first tour win since 2007.

In 2005 Hewitt reached the finals of the Australian Open, and the semifinals at both Wimbledon and the U. Open, but he has not returned to the finals of a Grand Slam tournament since. Hewitt began dating fellow tennis pro Kim Clijsters after they met at the 2000 Australian Open; the couple became engaged in December 2003 but split in 2004.

At the Australian Open, he was defeated in the fourth round by Swiss Roger Federer.

At the French Open, he was defeated in a quarterfinal by Argentine Gastón Gaudio.

Hewitt married Australian soap opera star Bec Cartwright in July 2005.

Their daughter, Mia Rebecca Hewitt, was born on 29 November 2005.

Hewitt became the first defending Wimbledon men's champion in the open era to lose in the first round.

Only once before in the tournament's 126-year history had a defending men's champion lost in the opening round, in 1967, when Manuel Santana was beaten by Charlie Pasarell.

For his third straight year, He qualified for the year-end Tennis Masters Cup, held in Shanghai, and successfully defended his title by defeating Juan Carlos Ferrero in the final.