Winston confirmed the decision in a statement issued late Wednesday morning by The Legacy Agency, which will represent him. Winston's father, Antonor Winston, had told ESPN earlier Wednesday that his son had decided to enter the draft after initially planning to announce the decision after Monday's College Football Playoff National Championship presented by AT&T.
"After weighing this decision with my family and friends, I have decided to declare for the 2015 NFL Draft and forgo my remaining eligibility at Florida State," Winston said in the statement. "I reached this very difficult decision after careful consideration and long thought, realizing how difficult it would be to say goodbye to my family at Florida State. I am eternally grateful for the opportunity to wear the garnet and gold and have greatly enjoyed my time as a Seminole, both as an athlete and a student in the classroom."
Antonor Winston said his son received a first-round grade from the NFL draft advisory committee.
ESPN NFL Draft Insider Mel Kiper Jr. has Winston rated as the second-best quarterback behind 2014 Heisman Trophy winner Marcus Mariota and the sixth player overall on his latest Big Board. Kiper thinks that Winston has special pocket instincts and the necessary vision, size, arm strength and athleticism to make it in the NFL.
In a conference call with reporters Tuesday, ESPN's Todd McShay said he believes that Winston is a better pro prospect than Mariota.
"[Florida State quarterback] Jameis Winston, to me, is the better prospect," McShay said. "Marcus Mariota is still a very good prospect but needs developing. They both have a chance to be great. But they both come with red flags. Winston's red flags are off the field."
Winston wrapped up his redshirt sophomore season with a loss to Oregon in the Rose Bowl Game presented by Northwestern Mutual. He was 26-1 as a starter and led Florida State to the national championship last season.
While off-the-field incidents swirled throughout much of his time at FSU, Winston's numbers were among the best in college football when he was on the field. Winston ranks fourth in touchdown passes (65), fourth in passing yards (7,964) and second in passes of 20 yards or more (124) since the start of the 2013 season.
Winston's statistics fell off this season as he threw for 3,907 yards, 25 touchdowns and had 18 interceptions. He also rushed for 65 yards and three touchdowns.
"I will always take pride in leading our team back to national prominence and am confident that my returning teammates will continue the success for many years to come," said Winston, who thanked Seminoles fans, teammates and the entire coaching staff in the statement.
Jimbo Fisher called it a "blessing" to coach Winston.
"He's one of the unique players that I've ever had the privilege to coach," Fisher said in a statement. "He embodies what you as a coach want as a person, a student and a player. He's a genuine and honest guy. He's one of the greatest players in Florida State history. I want to thank him for the way he represented himself and the organization in so many tough situations and the professionalism in which he handled the ability to be such a great teammate to his teammates and always put them and the program above himself. That's a very unique ability to be able to do especially at his age."
The biggest knocks on Winston remain his off-the-field scandals, which included a rape allegation for which he was not charged. In December 2014, Florida State held an internal student code of conduct hearing regarding those allegations in which an independent arbiter ruled that there was not enough evidence to find Winston guilty.
The accuser's lawyers filed a civil lawsuit against Florida State on Wednesday, alleging it didn't properly protect her Title IX rights.
Winston also served a one-game suspension earlier this season for yelling a vulgar phrase in an on-campus dining area.
McShay on Tuesday acknowledged that Winston's off-the-field trouble might scare away some NFL teams.
"The cons about Jameis Winston are, what are you getting with maturity and with the individual off the field? Can he stay out of trouble? And can he handle himself in a manner where you feel comfortable giving him $25 million or $30 million and tagging him from day one as the face of your franchise? It's hard, man. I don't know the answer right now," he said.
Winston could become the third Florida State quarterback selected in the first round in the past five years, joining Christian Ponder in 2011 and EJ Manuel in '13. According to ESPN Stats & Information, it would be the first time in the common draft era (since 1967) that three quarterbacks from the same school were picked in the first round in a five-year span.
"As I embark on the next challenge of playing in the NFL, I look forward to contributing to a long line of successful alumni at the next level," Winston said in the statement. "I want you all to know that I will make Seminole Nation proud and continue to bring the passion and love for the game you all have seen in Doak Campbell since my first day as a 'Nole. Thank you for making my time in Tallahassee some of the best years of my life."
Winston's father said that initial plans to delay an announcement were scuttled by extensive media attention and that after Jameis Winston prayed on the decision Tuesday night, he felt comfortable with his plan to leave for the NFL.
The QB will be represented by Greg Genske of The Legacy Agency. Winston, a pitcher at FSU who was drafted by the Texas Rangers in the 15th round in 2012, also chose that agency to advise him in baseball. NCAA rules allow baseball players to have advisers and maintain their eligibility.
ESPN's Darren Rovell and Adam Caplan contributed to this report.