In the same year he was a member of the Ukrainian national youth team, which won the U-16 Chess Olympiad in Artek, Ukraine.

In 2005 he tied for 1st–5th with Levon Aronian, Kiril Georgiev, Alexei Shirov and Emil Sutovsky in the Gibraltar Chess Festival.

In 2007, he tied for 1st–6th with Vitali Golod, Mateusz Bartel, Yuri Yakovich, Michael Roiz and Mikhail Kobalia in the 16th Monarch Assurance Isle of Man International tournament.

[6] At the 39th Chess Olympiad, held later in the same year in Khanty-Mansiysk, Efimenko won the team gold medal and an individual silver playing board 4.

[1] In July 2013, he tied for 1st–4th with Igor Kurnosov, Mikhailo Oleksienko and Avetik Grigoryan in the Masters tournament of the Abu Dhabi Chess Festival.