The 28-year-old striker debuted in the 2005 English Premier League under Harry Redknapp, who is one of the senior most managers in English professional football.
Keene had a successful career in Sweden between 2007 to 2013 and was considered one of the brightest stars in the Swedish League.
After signing for NEUFC, Keene said, "I am very proud to be part of NorthEast United FC and it's great to know that the North East is the powerhouse of Indian football and that the people here are very educated about the game as well."
"All of us are training very hard at the moment and the training is fantastic, especially working under an experienced coach like Ricki Herbert. We are excited about the start and hope that this new league will take Indian football to the global stage.