The 24-year old Swiss international has joined the Foxes on a season-long loan, reuniting with manager Sven-Goran Eriksson who he worked with at Manchester City.
Eriksson today confirmed the capture of Fernandes, who he describes as a versatile midfielder.
"Gelson is a hugely experienced footballer and we are delighted that he is joining us at King Power Stadium," he told the club's official website.
"He is an all-round midfielder, who can sit and protect the defence, but he is also a box-to-box player.
"He has great energy and determination, qualities which will help us this season."