On 18 June, his 19th birthday, he won his first ATP title, defeating Max Mirnyi in the final of the grass-court tournament at Nottingham, England.
He then made his Davis Cup debut against Russia in July, where he won his first rubber against Igor Andreev, but lost his second against Nikolay Davydenko. In 2006, Gasquet had a slow start after a first-round defeat by Tommy Haas at the Australian Open.
Having struggled to find any form after his comeback during the clay season, Gasquet went out in the second round of the French Open to David Nalbandian.
Following a disappointing opening half of the season, in the space of three weeks he successfully defended his title at Nottingham, lost in a first-round meeting with Roger Federer at Wimbledon, and won his second title of the year on clay in Gstaad.
In October, he won his third title of the year, this time on indoor carpet in Lyon, completing his achievement of reaching finals on all four surfaces during the year.
His season ended when he withdrew in the third round of the Paris Masters due to illness.
As a result, he became the youngest French player ever to defeat a world No. However, the eventual champion Rafael Nadal defeated him in the semifinals.
Gasquet reached his first final of the season two weeks later at Estoril, but the up-and-coming Serbian player Novak Djokovic got the better of him in three sets.He was also the youngest player to finish in the year-end ATP top 200.In 2004, he reached his first ATP tournament final at Metz, but lost to fellow countryman Jérôme Haehnel.Gasquet had to miss the last two months of the season because of an elbow injury. He later avenged this defeat in the Davis Cup first-round tie against Germany, where he beat Haas in five sets.However, he lost both his singles rubbers in a quarterfinal tie versus Russia and suffered an abdominal injury in that tie which left him out of action for a month.