Maya Moore of Connecticut won the women's award for the second straight year.
Fredette received 3,761 votes in the poll of nearly 10,000 national media members who cover the sport. Walker was second with 3,356 in voting that closed before the Final Four of the NCAA tournament.
Fredette accepted the 35th annual trophy from Jim Wooden, the son of the late UCLA coaching great during a ceremony at the Los Angeles Athletic Club.
"I definitely enjoyed the ride," he told reporters. "I had a great time being with my coaches and my teammates. It was the most fun I ever had in my life."
Jared Sullinger of Ohio State was third, followed by Duke's Nolan Smith, Arizona's Derrick Williams, Ben Hansbrough of Notre Dame, Marcus Morris of Kansas, JaJuan Johnson of Purdue, Kawhi Leonard of San Diego State and Jacob Pullen from Kansas State.
Fredette became the first BYU player since Danny Ainge in 1981 to win, adding the Wooden trophy to the collection he's picked up in recent weeks, including ones from The Associated Press and the Atlanta Tipoff Club.
"I have a pretty small house in New York, so I'm not sure I can fit them all in. It's been surreal. I've been all over and met a lot of great people," he said, naming Jerry West, Oscar Robertson, Clyde Drexler, and Olympic track and field star Carl Lewis.
The senior guard from Glens Falls, N.Y., broke Ainge's school career scoring record, finishing with 2,599 points. He had 15 30-point games and four 40-point efforts in his remarkable final season.
"We had quite a ride with Jimmermania," said BYU coach Dave Rose, who accompanied his star player.
Each of the top five men's finalists was on hand, and each chose his favorite Wooden quote. Fredette's selection was: "The true test of a man's character is what he does when no one is watching."
"I really took it to heart," he told the audience. "When you get better as a basketball player is in the offseason. You work hard without all the media attention and no one watching. It's all about that drive and all about that character when no one is watching."
Since BYU's season ended in the NCAA tourney's round of 16, Fredette has been working out in preparation for the NBA draft in June. He's chosen four finalists in his search for an agent, and plans to announce his selection next week.
Fredette, who sported a fresh haircut for the ceremony, denied speculation that he's engaged to his girlfriend of 1½ years.
"I'm not engaged," he said. "I've heard that many times."
Moore, a four-time All-American, ended her career as the Huskies' career scoring leader with 3,036 points, and ranked second in 3-pointers made and rebounds. Moore averaged 22.8 points, 8.2 rebounds, 2.3 steals and 4.0 assists this season.
She led the UConn to four consecutive Final Fours and two national titles, including its record 90-game winning streak that spanned three seasons.
Moore, who won last year, joined LSU's Seimone Augustus and Candace Parker of Tennessee as the only two-time winners of the award.
She received 678 votes. Britney Griner of Baylor was second with 566 votes.
Courtney Vandersloot of Gonzaga was third with 283. Stanford teammates Jeanette Pohlen and Nnemkadi Ogwumike were fourth and fifth. Pohlen got 198 votes to Ogwumike's 185 votes.
Moore received the trophy from Mark Llewellyn, son of the late award co-founder Duke Llewellyn. Vandersloot and Pohlen didn't attend because they're preparing for next week's WNBA draft.
Llewellyn and Wooden died within days of each other last year.
"This is a perfect way to celebrate their life and I'm just happy to represent," Moore said. "I'm so grateful to be involved one more year."
Michigan State's Tom Izzo was presented the Legends of Coaching award by Nan Muehlhausen, Wooden's daughter who attended for the first time since a falling out between her family and the award organizers several years ago.
Izzo led the Spartans to their 14th consecutive NCAA tourney appearance this season, where they lost to UCLA in the second round.