Experienced Jackson, 32, has signed a new one-year deal while academy product Massey has signed for a further two years.
Jackson is in his second spell with the Tigers having re-joined from Huddersfield before the 2010 season. He initially played for the club during the 2003 and 2004 seasons.
“I’m really pleased to be going round again; I’m really enjoying myself at Cas,” he said.
“I feel that I can still do it physically and I’m enjoying my Rugby as much as ever.
“There’s a good bunch of lads here and hopefully we can finish this season on a high and improve again next season.”
Signed from the Walton Warriors junior club initially for scholarship, 22 year-old Massey made his debut in 2007 as a 17-year-old and, having gained valuable first team experience through loan spells at Featherstone, York, Gateshead and Keighley, is now gaining more regular Super League action for the Tigers.
He has made 11 appearances so far this season and hopes to establish himself further during the duration of his new deal.
“I’m happy to be staying at Cas. I’ve come through the system here and I never really wanted to go anywhere else,” he said.
“There’s a really good platform here for the new coach to build on and I’m glad to be a part of the club’s future.
“I’ve worked hard to get to the position where I am now; getting more Super League game time and hopefully from here I will be able to become a first choice regular in the side over the next couple of seasons.”Jackson and Massey join fellow forward Stuart Jones in having signed new contracts with the club for next season at least.