Winston, who was the top overall pick of the 2015 NFL Draft, will earn $20.922 million.
The deadline for teams to declare the fifth-year option for players in that draft class is May 3.
Winston became the first quarterback in NFL history to throw for over 4,000 yards in each of his first two seasons.
The 24-year-old was hampered by a shoulder injury in 2017, limiting him to a career-worst 3,504 passing yards with 19 touchdowns in 13 games.
Winston has completed 939 of 1,544 passes for 11,636 yards with 69 touchdowns and 44 interceptions in 45 career games with the Buccaneers. He has also rushed for 513 yards with eight scores.
Off the field, Winston currently is under investigation by the NFL for allegations of groping made by a female Uber driver. Winston has maintained his innocence and former Florida State teammate and Philadelphia Eagles cornerback Ronald Darby said he was with the quarterback in the backseat of the car and nothing occurred.
General manager Jason Licht and coach Dirk Koetter have expressed frustration over the slow pace of the inquiry. Winston could face suspension under the league's broad player conduct policy.
Winston said he was grateful for the confidence expressed by co-chairman Joel Glazer at the NFL owners meetings in Orlando.
"It meant a lot to me because I know my work ethic for this organization, for this team is unparalleled," Winston said. "You know, every day I walk in this building, I'm trying to be the best I can possibly be and be the best for this organization so to have support of ownership, it really inspires me to continue to work hard and continue to be the leader that I am."