Kent has played 35 games in the red, white and black since joining the club from Melbourne at the end of 2018, with next season set to be the his fourth year at St Kilda.
The 27-year-old made seven appearances at AFL level in 2021, booting five goals.
Joyce has played a total of 10 games for the Saints since making his debut in 2018, doubling his games tally this season with five matches under Brett Ratten.
The Irishman has shown plenty of promise in defence for St Kilda since joining the club after a trial in 2016 following a move overseas to Australia.
Saints list manager James Gallagher expressed his delight in having the duo recommit their stay for another year.
“We were really pleased with Darragh’s development over the past few seasons,” he said, via the club's announcement.
"His versatility, competitiveness and athleticism give him the ability to man key posts at both ends, and has seen Darragh rewarded with opportunities in the senior line up this year.
“Dean’s power and strength are valuable assets for us.