Nikolaj Davydenko has won a total of 21 singles and 2 doubles ATP titles in his career. He was world No. 3 in November 2006, advancing to the semifinals twice at both Roland Garros and the US Open and also unexpectedly winning the year-end Masters in 2009. He was among the protagonists of Russia's triumph in the Davis Cup 2006.

Due to numerous injuries, he retired from competition in 2014, at the age of 33.

In 2005 he takes home only one tournament, but at Roland Garros he pushes himself to the semifinals, where he loses to Mariano Puerta, who was later disqualified for doping. His ranking now consolidated, Davydenko made further progress in 2006: he won five titles, reached the semifinals of the US Open, where he lost to Roger Federer, and also helped Russia win its second Davis Cup.

At the end of the year he finished in 3rd place in the ranking, behind only the dominators Roger Federer and Rafael Nadal. 2006 is also the year of his marriage to his partner Irina. On 16 October 2014 he communicated his withdrawal from competitive activity.