However, OM would be stripped of their domestic title, though not of the Champions League crown, due to their involvement in a domestic match fixing scandal, and a year later (1994) would suffer a forced relegation to the second division due to a related financial bankruptcy. Barthez's 1993-1994 season is seen by many as his best in le Championnat, his many saves and the goalscoring quality of Sonny Anderson allowed l'OM to finish second this year. He stayed with his club in Division 2 for the 1994-1995 season despite many offers from elite French clubs.
Well-known for being eccentric, he started out well for Manchester United. His first season was a triumph as he answered all the questions about how he would handle rainy Manchester compared to sunny Monaco. Barthez performed brilliantly throughout the season and became a crowd favourite. The fans loved his eccentric behaviour, his taunting dribbles and step-overs past opposing strikers, and most importantly, his remarkable reaction saves. Very often it was critical saves that kept United from defeat or dropping valuable points, helping United to the 2000-2001 Premier League title, which was United's third in a row. The only blemish being his failed attempt at "psyching out" West Ham United's Paolo Di Canio in the FA Cup 4th Round. Di Canio beat the offside trap, while Barthez stood still with his hand up expecting the referee to blow his whistle, or Di Canio to stop. Di Canio continued and scored the only goal of the game.
The 2001-02 season was split into two parts for him. The first half was a nightmare. The Frenchman seemed to be taking some unnecessary risks outside his penalty area, and his antics began to have consequences that allowed unneeded goals for opposing teams. He was at fault for two goals in a home defeat by Deportivo La Coruña in October 2001, Another couple of errors against Arsenal the following month put much pressure on Barthez. There was much speculation as to what was the source of Barthez's decline, and critics urged him to be dropped. However, Sir Alex Ferguson had faith in his goalkeeper and stuck by him. Consequently in the second half of the season, Barthez repaired his reputation with consistent, solid performances and the spectacular saves that he was famous for.
In 2002-2003 led to another Premier League crown for United. The season was a mixed bag for Barthez. One highlight was a fabulous save to deny Dietmar Hamann's 30 yard rocket at Anfield as United held on to win 2-1. In other games, he let goals go past him that shouldn't have done. Barthez was also widely criticised in United's exit to Real Madrid in the Champions League, especially for Ronaldo's opener which beat him at the near post. It would prove to be his last ever game with United as Sir Alex Ferguson's patience had finally run out. Barthez was dropped for the final 3 games of the season, with Roy Carroll taking his place.
Barthez was involved in a controversy due to his actions during a friendly match between OM and Morocco's Raja Casablanca on 12 February 2005. With 10 minutes left, an OM player was sent off, and a brawl erupted between players on the pitch. Barthez was reported for spitting on the Moroccan referee. On 21 April, Barthez was summoned to a hearing before the disciplinary committee of the French Football Federation; the following day, he received a six-month suspension, with the last three months being suspended. In an unusual move, the federal council of the FFF appealed the suspension, arguing that the punishment should have been for a minimum of six full months. Eventually, his suspension was extended to six full months due to political pressures.
On 29 April, Nantes chairman Rudi Roussillon announced that following an altercation with a Nantes fan, Barthez had left the city with his family. The next day, Barthez confirmed that he had quit the team, and the club terminated his contract. Barthez denied that he was planning to retire, and in an article for French daily L'Équipe, he said that he was looking for another contract for at least 2 years. Since then Barthez has been linked with numerous clubs but nothing has ever materialised and he has had to face never playing professional football again.
On 25 January 2008, after an interview with Setanta Sports, Barthez says he plans to race Porsche GT 3s and to play beach soccer in the future.
In the 1998 World Cup which was hosted by his home country, Barthez conceded only two goals in seven games and bagged the Yashin Award as the best goalkeeper of the tournament. Barthez was also well-known during the tournament for letting teammate and good friend Laurent Blanc kiss his shaved head before the start of every match, supposedly for good luck. Barthez was an integral part of his national team's inaugural triumph which also made it the first time in 20 years that a host had won the World Cup; the highlight being a 3-0 shutout of defending champion Brazil in the finals. During the game, Barthez made a spectacular save on Brazilian superstar Ronaldo, doing his trademark leap/step-over the attacking striker to grab the ball, which injured Ronaldo in the process. Barthez was afterwards one of the most popular national players in France, second to Zinédine Zidane.
France had a slow start in the group stage, drawing their first two games and putting their playoff chances at risk. Fortunately, Barthez's team found their form and won their final round robin match 2-0 to advance to the next stage, where they upset heavily favoured Spain 3-1 in the round of 16.
In defeating Brazil, 1-0 on 1 July 2006, Barthez, having made only one save in the game, became the first keeper to blank the Brazilian team in consecutive World Cup finals matches, the first being the 1998 final (3-0). France is now one of only two nations (along with Argentina) to have shut Brazil out twice in the World Cup finals, and the first to have done it in consecutive matches, both times with Barthez in goal.
Barthez again kept a clean sheet in the semi-final against Portugal (with Zinédine Zidane's penalty shot the winning goal), though he appeared in questionable form. A few minutes from time, he spectacularly spilled a free-kick which Luis Figo recovered, heading over the bar although unchallenged. He did, however, redeem himself in injury time when a French defender fumbled the ball, enabling a Portuguese player to mount a last-moment attack. Barthez scrambled out of the net and blocked the first shot.
During the final against he briefly captained his team for the remainder of the second period of extra time after Zidane was sent off. During the penalty shootout, neither he nor his Italian counterpart Gianluigi Buffon made a save, and France striker David Trezeguet's missed shot ultimately proved decisive.