The Browns had been expected to take a quarterback and had insisted Mayfield was under consideration through the pre-draft process. Most speculation still centered on USC's Sam Darnold and Wyoming's Josh Allen, but momentum for the Browns' favoring Mayfield started to build in the last few days.
"My story is something I only could have dreamed of. To actually be a reality, it's amazing," Mayfield told reporters Thursday night.
Cleveland also had the fourth pick Thursday and used it to select Denzel Ward, a cornerback from Ohio State. General manager John Dorsey said he liked Ward's ability to play man-to-man, press coverage, which the Buckeyes ask of their corners.
"I am very confident in my ability. I am looking forward to that pressure," Ward told reporters after his selection. "Being at Ohio State, there was pressure all the time there. Everybody is on edge there, so it is kind of nothing new having that pressure on me, and I look forward to taking that challenge and seeing what I can do at the next level."
Mayfield, who had a stellar college career at Oklahoma but also made headlines with his behavior on and off the field, will be tasked with turning around a Browns team that went 0-16 last season.
Mayfield joins a roster that has Tyrod Taylor as the starting quarterback and Drew Stanton as the backup. The Browns hope to play Taylor this season, allowing Mayfield time to learn and grow. Mayfield, though, said at the scouting combine he would never "settle" for a backup role.
"Tyrod Taylor is going to be our starting QB, first and foremost. It's understood by Baker that he has to come in and learn the NFL game," Browns coach Hue Jackson said after Mayfield's selection, adding, "We will do everything we can to put him in the best position to play."
Mayfield said he respects the fact that Taylor is the starter.
"That's a veteran that's been in the league, that's a guy I can learn from," he said. "I want to be the guy who comes in and helps change the culture of the locker room. I'm going to be myself and let the rest take care of itself."
The Browns have not made the playoffs since 2002, which is the longest active drought in the NFL. Since returning to the NFL in 1999, the Browns have had 28 different starting quarterbacks -- the most in the league during that span.
Mayfield led FBS with a 70.5 completion percentage in 2017, and he set a single-season record by averaging 11.5 yards per attempt. He threw for 4,627 yards with 43 touchdowns and just six interceptions.
But Mayfield also garnered negative attention in recent years for his on-field antics, which included making an inappropriate gesture toward Kansas' sideline and planting Oklahoma's flag on Ohio State's logo at the 50-yard line after the Sooners' victory over the Buckeyes.
Mayfield also was arrested last year in Arkansas on charges of public intoxication, disorderly conduct, fleeing and resisting arrest. He reached a plea deal last June and paid fines for several of the charges.
"I have no qualms about this guy whatsoever as a man and as a football player. I think he is a really good person," Dorsey said after selecting Mayfield. "This is a guy who has earned everything he has, from high school to college to here. For the Cleveland Browns organization, this was the best available player. The guy knows how to play the game and knows how to win. He really is a neat kid. He's humble. He really is humble."
Throughout the draft process, the Browns said they felt Mayfield had admitted to his mistakes and they were behind him. Dorsey even joked with Mayfield at the team's combine interview, asking how he liked food trucks, a reference to the February 2017 arrest that took place near food trucks. Thursday, Dorsey said the team's dive into Mayfield's background was so extensive he knows what Mayfield ordered at the food truck prior to the arrest.
"It's been a very entertaining back and forth with him (Dorsey), which makes it fun," Mayfield said. "He's been up front and honest about messing with me about my mistakes and I've been honest with him about what I learned from it, the fact that it shoudln't have happened."
"I have learned from my mistakes. I've grown up. I can be honest about my mistakes," Mayfield said. "I'm just excited I can be that way with them. On top of it, it shows that it's not about your size (height). It's about winning and the mentality and leadership quality."
Mayfield, who is from Austin, Texas, transferred from Texas Tech to Oklahoma after his freshman season. During his college career, he threw for 14,607 yards and had 131 touchdown passes and 30 interceptions. He also rushed for 21 TDs and caught another during his college career.