Love Rugby League reported that the back-rower was a target for Cas back in August.
Sene-Lefao said: “I’m really excited to be heading to the UK to join Castleford Tigers. I’m good friends with Ben Roberts and Junior Moors and they’ve both told me much such positive stories about the club and how passionate the fans are,”
“I’m ready now to take my game up to a new level and Castleford sounds perfect for me.
“I’m looking forward to playing for a club that plays such a big part in the community and my family and I are looking forward to the experience of moving overseas and getting to know the people of Castleford.
“We’re taking a family holiday right now but I can’t wait to make the move and knuckle down and show what I can do in pre season training.”
Cas head coach Daryl Powell said: “I’m delighted that Jesse has agreed to join us.
“I watched him play two years ago for Manly and I was really impressed with his skill, energy, enthusiasm and determination as a player.
Tigers CEO Steve Gill added: “Jesse is going to be a great addition to our pack.
“At 26 years of age we feel as though it’s the right age for him to develop into the cornerstone of our pack for years to come, and I’m sure he will be a big favourite with our fans.
“I would like to thank Cronulla Sharks for agreeing to release Jesse from his contract early to join us.”