In 1999, Elena Dementieva represented Russia in the Fed Cup final against the USA, scoring Russia's only point when she upset Venus Williams. 1999 was also the year in which she played her first Grand Slam main draws qualifying for Australian Open, Roland Garros and Wimbledon and getting a direct entry into the US Open. She managed to reach the second round at the Australian Open and Roland Garros, made a first round exit at Wimbledon, and managed to reach the third round of the US Open.

In 2000, she entered the top 20 by winning more than 40 singles matches for the second straight year and earned more than US $600,000. She reached her first Grand Slam semifinal at the US Open, losing to Lindsay Davenport and becoming the first woman from Russia to reach a US Open semifinal. At the 2000 Summer Olympics, Sydney, she won the silver medal, losing to Venus Williams in the final. In 2000, she was named the WTA tour's Most Improved Player.

2001 was the second straight year in which she finished in the WTA's top 20. During the year. she became the no. 1 Russian tennis player, a position previously held by Anna Kournikova since December 1997.

2002 was her best year in doubles. Partnering Janette Husarova of Slovakia, she reached her first Grand Slam final at the US Open and won the Year End Championships.

In 2003, she played the most tournaments among top 10 players (27) and won approximately US $900,000 in prize money. At Amelia Island, she won her first WTA tour title, defeating Amanda Coetzer, Daniela Hantuchov�, then world no. 1 Justin Henin, and world no. 2 Lindsay Davenport. She was the lowest seed (10th) to win the tournament in its 24-year history. In 2003, she also won back-to-back titles in Bali and Shanghai, defeating Chanda Rubin in the final in both events. She finished 2003 in the top 10. In addition, she reached the semifinals of the Wimbledon doubles with her friend and compatriot Lina Krasnoroutskaya, beating the Williams sisters on the way.

In 2004, Dementieva had a breakthrough year. At Miami, seeded 5th, she eliminated former world no. 1 Venus Williams, who was seeded second, in the semifinal, then faced former world no. 1, top seed and two-time defending Serena Williams. Serena won the match. On April 5, she reached her highest singles ranking at sixth in the world. With no. 5 Myskina and no. 9 Nadia Petrova, it was the first time that three Russians appeared in the WTA top 10 simultaneously. In May, at Roland Garros, she reached her first Grand Slam final, defeating former world no. 1 Lindsay Davenport in straight sets on the way. She lost to compatriot Anastasia Myskina in the first all-Russian Grand Slam final. Former Russian president Boris Yeltsin watched the match. Incidentally, the last female Russian Grand Slam finalist was Dementieva's coach, Morozova at 1974 Roland Garros and Wimbledon. Later that year, at the US Open, she reached her second Grand Slam final, defeating Jennifer Capriati and Amlie Mauresmo on the way. 19-year-old countrywoman Svetlana Kuznetsova defeated Dementieva in straight sets in the final, becoming the third consecutive Russian woman first-time grand slam winner.

She reached the semifinals of the 2005 US Open where she lost to French woman Mary Pierce 6-3 2-6 2-6. Partnering Flavia Pennetta of Italy, she reached her second doubles final at the US Open. Elena led Russia to repeat as Fed Cup champions, beating France 3-2. All three points came from Dementieva: She avenged her loss to Mary Pierce, beat Amlie Mauresmo, then won the deciding doubles match with partner Dinara Safina.

She has won more prize money than any other female Russian tennis player in history and has won more Grand Slam matches than any Russian tennis player.