Tuncay's transfer to Middlesbrough has been finalised after he was granted a work permit.
The Turkey international agreed a four-year deal with Boro last month and then returned to his native country to wait for his application to be processed.
He is now expected to join up with his new team-mates in time to fly out for a pre-season tour of Austria.
Tuncay joins on a free transfer following the expiration of his contract at Fenerbahce.
Gareth Southgate has also brought in Jeremie Aliadier this summer and completed the permanent signing of Jonathan Woodgate, but he still wants his squad to have greater strength in depth.
"All I can say is we are actively looking to improve the team and improve the squad," said the Boro manager.
"We have been watching several different players in different positions.
"Obviously at right-full-back we have lost Abel Xavier and Stuart Parnaby, and Tony McMahon is still recovering from a broken leg, so we are very short of cover and competition in that position, although we have some good youngsters coming through.
"I still feel we need to add a couple of players. We are looking very much to do that over the coming weeks, and the sooner we can get them in, the better.
"But it is great to have, with Jonathan, three new signings in place already, and to know we have built already on what we did last season."
Source : www.skysports.com
By Lewis Rutledge - Created on 4 Jul 2007
