NC State announced last weekend that Lewis would look to play elsewhere. In a phone interview with The Associated Press, Lewis said he looked at Purdue, Xavier, Charlotte, Gonzaga and UAB before choosing Butler.
"They just made it feel like home up there," Lewis said. "All the players, I fit in really well with them. ... I just felt like it would fit my style of play great -- the way they get out in transition and have a lot of screen-and-rolls."
Lewis said he informed the Butler coaches of his choice earlier Friday.
The 5-foot-11 guard split time with touted freshman Anthony Barber before taking over the starting job for the last 14 games. The Wolfpack (22-14) upset Syracuse in the ACC tournament and beat Xavier in the First Four of the NCAA tournament before falling to St. Louis in overtime.
Lewis averaged 4.4 points and a team-best 3.8 assists, but his best asset was protecting the basketball -- he had just 38 turnovers in 36 games -- while setting up high-scoring forward and ACC player of the year T.J. Warren.
Lewis originally committed under former coach Sidney Lowe and had a tough time finding minutes under Mark Gottfried as a freshman behind Lorenzo Brown for a team that went one-and-done in the NCAA tournament.
"I have no bad feelings at all," Lewis said. "I love NC State. I'll always love NC State. I mean, I committed here my junior year and I wouldn't have committed here if I didn't love the school. ... But I felt like it was the best move for me to move on."
Lewis said he'll attend summer school at Butler and work to bulk up his 170-pound frame to better handle physical play.
Lewis arrived at NC State in 2012-13 as part of a recruiting class of three McDonald's All-Americans that included Warren and Rodney Purvis.
Warren -- who averaged a league-best 24.9 points -- is still mulling whether to enter the NBA draft. Warren's father Tony, a former Wolfpack player, said Thursday that he wants his son to take his time to be "100 percent sure" and an announcement could come Tuesday.
Purvis transferred to Connecticut after last season and sat out this year.