Ireland duo Jordi Murphy and Will Addison have signed new two-year deals with Ulster.
Back row Murphy and utility back Addison were coming to the end of their contracts but have agreed new terms while the season has been suspended due to the coronavirus pandemic.
Jacob Stockdale was among the players who had already opted to remain with the Pro14 club, who have also signed fly-half Ian Madigan and scrum-half Alby Mathewson.
Head coach Dan McFarland said after Ulster's squad for next season was announced: "Our desire to build on the successes of this season to date is evidenced in our strong investment in talent from the current squad.
"Although it's an uncertain time for rugby, and all sport, I am confident our selection will stand us in good stead for when we are able to safely start the new season."
He added: "Looking to the future, we look forward to welcoming the new additions to the squad, who are set to bring their own unique skills and talent, as we move towards a time when the 2020-21 season can kick-off."