Philippoussis has had a minor career in modelling and starred in the American reality television dating show Age of Love.

Philippoussis also finished as junior doubles champion with Ben Ellwood in Australia, Wimbledon, and Italy.

In January 1999, Philippoussis and Jelena Dokić won the Hopman Cup for Australia, defeating Sweden's Åsa Carlsson and Jonas Björkman in the final tie.

During that match, Philippoussis suffered a moderate cartilage tear in his left knee and underwent arthroscopic surgery four days later.

2 Sampras 8–6 in the fifth set at the French Open in a first-round match, but lost in the fourth round to Juan Carlos Ferrero.

He appeared in his second Olympic Games in Sydney, losing in the third round to eventual gold medalist Yevgeny Kafelnikov.

Philippoussis has always claimed to be proud of representing his country in Davis Cup, but personal differences with John Newcombe and Tony Roche interfered with his commitment early in his career.

Despite several highly publicised feuds, Philippoussis played a large part in giving Australia their 27th Davis Cup triumph—second only to the United States with 31—but it was their first since 1986.

Injuries plagued Philippoussis's availability for Davis Cup and was the cause of a public rift between team-mates Patrick Rafter and Lleyton Hewitt.

Rafter publicly accused Philippoussis of jerking the team around after he withdrew from a Davis Cup tie in late 2000.

By then, Pat Rafter had retired, and John Fitzgerald and Wally Masur were the new Davis Cup captain and coach.

On 30 November 2003, he defeated Juan Carlos Ferrero of Spain to win the fourth match of the Davis Cup final in Melbourne, securing the title for Australia.

After shouldering most of the blame for losing Australia's Davis Cup tie with Sweden with an unexpected below-par performance, Philippoussis struggled through to the Wimbledon fourth round in June 2004.

From Wimbledon in June until the end of the season in October, he failed to win a single ATP tennis match and finished with one of his lowest rankings since turning professional in 1994.

After some controversy over his wildcard selection after a disappointing 2006 Australian Open, Philippoussis made more headlines when he again earned entry into the 2006 Wimbledon.

He had a fantastic run in the tournament, getting to the final, where he defeated Justin Gimelstob in straight sets to claim his first title in almost three years.

He confirmed to Sydney's Daily Telegraph on 23 August 2006, that he "parted ways with" his father as his coach and rehired Peter McNamara in an attempt to revive his career.

Philippoussis then lost his second match to Sam Groth, 4–6, 3–6, but due to other players' injuries, he advanced to the quarterfinals, where he was to play Rameez Junaid.

Philippousis appeared in a pro tour match for the first time since November 2006, when he lost to fifth seed Michael Yani, 4–6, 4–6, in the first round of the Challenger of Dallas.

Philippoussis also played doubles in the tournament with Ryan Harrison, winning the first round to make it to the quarter-finals before losing to the second seeds Austin Krajicek and Rajeev Ram.

At first Philippoussis, unaware of the special format of the show, was shocked at the ages of the "cougars" as the older women were called.

In the end, Philippoussis chose Amanda Salinas (the 25-year-old Nashville Predators dancer) because it "wouldn't work out" with Jen, the 48-year-old assistant to Jerry Buss.

[16][17] The couple's relationship ended in controversy when newspapers reported Philippoussis had been unfaithful with famed American socialite Paris Hilton.

In a writ lodged with the Supreme Court on 15 May 2009, it was alleged Philippoussis took out a loan through his company Mergis Pty Ltd which he personally guaranteed.

[20] In September 2009, his father Nick Philippoussis – a tennis coach and accused sex offender[21] – also faced the threat of bankruptcy over financial institution debts.

[26] In July 2023, Philippoussis was fined US$10,000 by the International Tennis Integrity Agency for breaching betting sponsorship rules.