Derby-born Camp, 26, qualifies through his grandfather and could now come into contention for the Euro 2012 qualifiers against Serbia and Slovenia next month
Northern Ireland manager Nigel Worthington is pleased to have Camp on board after FIFA gave the player the go-ahead.
He said: "I am delighted that clearance has come through for Lee to play for us. It has taken a bit of time, but the patience has paid off.
"This is a big plus and it is testament to the quality we have in the squad that players of Lee's calibre want to come and play for Northern Ireland.
"I have spoken to Lee and he is absolutely delighted that he has been cleared to represent the birthplace of his grandfather."