Anderson announced his decision Monday at a news conference at Gallagher-Iba Arena, saying "I believe now is the time for me to pursue my dreams by playing in the NBA."
Anderson averaged a Big 12-best 22.3 points per game while leading the Cowboys into the NCAA tournament for a second straight year. The versatile 6-foot-6 guard was an overwhelming choice as the league's player of the year, earning the selection ahead of such stars as Kansas' Sherron Collins and Cole Aldrich, and Kansas State's Jacob Pullen.
"I believe now it's time to test my basketball skills against the best players in the world," Anderson said. "I have worked hard to improve my abilities over the last three years. ... I believe that I am fully prepared both athletically and emotionally for the challenge of playing in the NBA."
The soft-spoken Anderson hesitated for a moment when he was asked where he hoped to be taken -- and coach Travis Ford answered for him.
"First," Ford said, drawing laughs from an audience of students invited to the news conference.
Anderson followed by saying he wanted to be among the lottery picks in the first half of the draft's first round.
"This decision was difficult because the past three years have been a great experience for me here," Anderson said. "I have grown so much as a person and as a basketball player, and we have won a lot of games and went to the NCAA tournament the last two seasons."
A former Arkansas high school standout who was named a McDonald's All-American, Anderson was recruited to Oklahoma State by former coach Sean Sutton before spending his last two seasons under Ford's tutelage. He increased his scoring average dramatically from 13.3 points as a freshman to 18.2 last year and was considered a potential first-round NBA draft pick even then.
Instead, he returned and focused on adding a stronger driving element to go with his accurate 3-point shooting. He said he benefited both from teammates refusing to take it easy on him and Ford developing an individual program for him to follow. He believes now he's more prepared to deal with a lengthy NBA season.
"Last year, I wasn't aggressive enough and I don't think I was mentally ready enough to go," Anderson said. "I think this year, coming back, it helped out a lot."
Anderson, who met with Ford to finalize the decision on Sunday night, said he had not yet hired an agent but plans to do so. If he does not hire an agent, Anderson would still be eligible to return for his senior season.
Anderson admitted there was a tiny bit of temptation to return and see if the Cowboys could make a deeper run in the NCAA tournament next season after a disappointing 64-59 loss to Georgia Tech in the first round on Friday night.
"It wasn't how I wanted to go out as a Cowboy," said Anderson, who missed all six of his 3-pointers and finished with only 11 points. "It happened like that but it wasn't like I planned for it to be. It was a very frustrating game and no question after that, it started to cross my mind to get back to that point again because I know how good our team was and I think we were better than we played."
Despite that lackluster finish, Anderson concludes his career as one of the most accomplished players in Oklahoma State history. He ranks behind only Byron Houston, Bryant "Big Country" Reeves and Adrian Peterson on the career scoring list and his 17.9-point average is second only to Houston.
No player has scored more points over his first three years at Oklahoma State.
"He's been a fine and perfect example of what we want this basketball program to be about, not just as a player but as a person," Ford said. "That's what I'm going to miss is just coaching every day a guy who you know you're going to get his best effort and you know you're going to have fun doing it because he's just a tremendous, tremendous, tremendous person."
Anderson said he considered his selection to the Big 12's all-academic team to be his proudest achievement at Oklahoma State, and he intends to honor his promise to his mother to eventually earn his degree.
"It really doesn't start with basketball. Every player has a different ability when it comes to what they can do on the court," Ford said. "We don't ask everybody to do what James was able to do for us.
"What I'm going to miss probably the most was somebody who was maybe the most coachable young man I've ever been around. I've been around him for two years, and in two years I've never -- not once -- ever had to call him into my office for anything he'd done wrong."