Fozzard, 33, has signed a one-year deal whilst Emmitt, 21, joins on a two-year deal.
Tigers boss Terry Matterson said: “Fozzie has had a long and illustrious career in the game and his experience will be vital for our young guys. His strength is his go forward and we are looking forward to playing off the back of him.
“On Jacob, we are very excited about his capture. His form for Saints over the last seven or eight weeks has been outstanding and he was a much sought after player by other clubs.”
Fozzard will arrive at The Jungle with a wealth of experience, having seen Super League action with Leeds, Huddersfield, Warrington, Hull KR and most notably St Helens. During five successful seasons over two spells at Knowsley Rd, Nick has won three Challenge Cups and two World Club Challenges, plus international honours with Great Britain and a place in the 2007 Super League Dream Team.
Fozzard has spent five seasons at Knowsley Road in two spells, picking up three Challenge Cup winners medals and two World Club Challenges. He has previously played for Leeds, Huddersfield, Warrington and Hull KR.
He said: “I’m really looking forward to joining the Tigers. I have a number of friends there and as a local lad, I know the club well and the rivalries it has as I also played in one or two of their derby’s when I was at Leeds.
“It is always a great atmosphere at the Jungle with good crowds and I like the way they play, so I’m just looking forward to giving my best for Classy Cas.”
Emmitt has spent the 2010 season on a dual-registration deal with Leigh Centurions.
He said: “Castleford are a big club with some good players and there should be some real competition for places up front.
“I could have stayed at St Helens and there were options at other clubs but Terry Matterson has a good reputation and I felt this move was a good opportunity to move my career forward.”