The junior-college quarterback from Southwestern, Calif., has moved into the dorms at U of L, enrolled in classes and will begin when the spring semester starts.
"It's a good feeling," said Nelson, who had a going-away party on Friday and boarded a plane early Saturday morning for Louisville.
Nelson, who has two years of eligibility remaining, will be able to participate in spring practice with the Cardinals.
"After watching the Sugar Bowl, it only made me want to get there more," Nelson said. "That was so much fun. Being around the program for a month or so, getting to know those guys, I knew they were going to win.
"Now, we're just going to keep getting better and better recruits."
With Teddy Bridgewater as the starter, Nelson will compete with redshirt freshman Will Gardner and true freshman Kyle Bolin next season for the backup spot. Gardner and Bolin are both coming off knee injuries.
"It's a great situation for me," Nelson said.
Nelson, who only other visit was to Division II Northwood, threw for 2,833 yards and 28 touchdowns while completing 58 percent of his passes and throwing just eight interceptions. He threw for 1,639 yards and 11 TDs as a freshman.
At Southwestern, Nelson plated for head coach Jim Bonds, who is a well-regarded coach and former UCLA quarterback. Bonds was the quarterback between Troy Aikman and Tommy Maddox at UCLA.