The ACC announced Wednesday that its presidents and chancellors unanimously voted to add Louisville as the replacement for Maryland, which will join the Big Ten in 2014.
Louisville athletic director Tom Jurich was concerned the Cardinals would be left behind in a constantly shifting landscape.
"You always worry about that, there's no question about it—especially when you're sitting in our chairs," Jurich said in a teleconference. "But I think when you look at what we've done and the body of work, I think it was very well worth it to wait because we were able to get what we wanted.
"We feel it's the best fit for this university."
Louisville was a candidate to join the Big 12 last year before that league took West Virginia, though Maryland's unexpected announcement last week created a new opportunity for both the school and the ACC.
But it wasn't a lock for the Cardinals.
A person familiar with the situation told The Associated Press that ACC leaders also considered Connecticut and Cincinnati over the past week before the vote to add Louisville during a conference call Wednesday morning. The person spoke to the AP on condition of anonymity because the ACC hasn't released details of the expansion discussions
The Cardinals will bring a tradition-rich men's basketball program, a solid football program and a college-focused market to the ACC.
"When you look at Louisville, you see a university and an athletic program that has all the arrows pointed up—a tremendous uptick there, tremendous energy," ACC Commissioner John Swofford said. "It's always an overall fit in every respect and I think that's what we found."
Louisville is the fourth school in 15 months and seventh in the past decade to leave the Big East for the ACC. Pittsburgh and Syracuse announced their move in September 2011 and will join the league next year, while Notre Dame said two months ago that it would eventually join in all conference sports except football.
Most of Notre Dame's non-football sports have competed in the Big East since 1995.
"We had incredible success in that conference," Jurich said of the Big East. "But when it began to deteriorate, we felt that all our options were pulled away from us and we had to look and we were forced to look.
"To see a lot of your peers moving around you and leaving nobody to schedule, it was very, very difficult for us to see and a very once-proud conference I think was in a very difficult position."
Politicians around Kentucky cheered the move.
Louisville mayor Greg Fischer issued a statement calling the ACC's decision "a fantastic development for the university, the city and the state." U.S. Senate Republican leader Mitch McConnell of Kentucky said in a statement the move was a credit to Jurich's leadership of the athletic department.
It's unclear exactly when Louisville will join the ACC. Swofford said that would have to be worked out between the school and the Big East. He also said the league is comfortable staying at 14 full members with the addition of Louisville.
The Big East has a 27-month notification period for any member that wants to leave. The Big East has shown a willingness to negotiate, as it did with Pittsburgh and Syracuse, who paid $7.5 million each to get out early when the exit fee was $5 million.
The Big East has since increased that fee to $10 million.
This latest rapid-fire round of realignment was set off last week by the Big Ten's additions of Maryland and Rutgers, which will join that conference in 2014.
On Tuesday, the Big East added Tulane for all sports and East Carolina for football only, also beginning in 2014.
In a statement, Big East Commissioner Mike Aresco wished Louisville well and said the league's additions are important for its future.
"We are committed to a vibrant and dynamic future for the Big East Conference," Aresco said.
Louisville's addition will add some extra juice to what's already one of the nation's premier conferences for men's basketball.
Louisville, currently ranked No. 5, brings a program that has won two national championships and reached its ninth Final Four last season. In addition, Rick Pitino will give the league another marquee coaching name alongside Duke's Mike Krzyzewski, North Carolina's Roy Williams and soon Jim Boeheim of Syracuse.
The school's football program is a win away from earning a BCS berth. Charlie Strong's Cardinals travel to Rutgers on Thursday night for a game in which they could clinch the Big East's BCS bid.
The ACC's decision to add Louisville is a blow for Connecticut, which had been looking for a landing spot since Pittsburgh and Syracuse announced their Big East exits. UConn President Susan Herbst had indicated that an invitation to join that ACC is something the school would welcome.
"We will be athletically successful, regardless of our conference, because of our successes in NCAA competition," Herbst said in a statement. "... I realize this is a difficult day, but when we focus on research, discovery, and student success, we'll never go wrong."
AP Sports Writer Joedy McCreary in Raleigh, N.C., contributed to this report.