Camp, 26, told the Irish FA last summer that he was keen to declare for Northern Ireland and his eligibility has now been successfully processed.
"I am thrilled that I am now able to play international football for Northern Ireland," said Camp who qualifies through a grandparent.
He has played five times for the England Under-21 team.
Camp added:"I am looking forward to the opportunity to join up with the squad."
"It seems like I have been waiting forever for the relevant paperwork to be sorted out with Fifa.
"I would like to thank Nigel Worthington for his patience and for giving me the chance to become involved in the Northern Ireland team."
Worthington spoke of his "delight" at getting Camp on board.
"It has taken a bit of time, but the patience has paid off," said Worthington.
"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."
Camp kept 19 clean sheets for Forest last season and played for England Under-21s but his hopes of earning a call-up to Fabio Capello's squad were dashed.
Veteran Birmingham keeper Maik Taylor, 39, is the current Northern Ireland number one.
Source: BBC Sport