The Tampa, Florida, native, who turns 37 on Saturday, has no previous managerial experience, yet the Rays are confident he has what it takes to be successful.
The Rays took to Twitter to welcome their new manager.
"It came down to the energy, the poise that he has, the confidence, but the open-mindedness that goes along with it. That's a rare combination to have in an individual," president of baseball operations Matt Silverman said.
Cash wowed the team during a final interview that lasted half a day. He becomes the youngest active manager in the majors, taking over a team that made the playoffs four of the past seven seasons under Maddon.
"After 12 hours we were pretty drained and it felt like Kevin was just getting started," Silverman said.
A former catcher who played with five major league teams, including 13 games for Tampa Bay in 2005, Cash served as Terry Francona's bullpen coach in Cleveland the past two seasons.
He also interviewed recently for the vacant managerial position with the Texas Rangers. He thought that experience helped when the Rays included him on an initial list of 10 candidates.
"It wasn't something I was anticipating at this stage. But as I started preparing for the Texas opportunity, I almost kind of gained momentum, gained some confidence," Cash said. "I was able to really process some thoughts."
Tampa Bay went 754-705 in nine seasons under Maddon, making the playoffs four times, winning two AL East championships and the 2008 AL pennant -- all while operating under the constraints of one of baseball's lowest payrolls.
The Rays finished 77-85 this year, ending a stretch of six consecutive winning seasons. Maddon was under contract through 2015, but exercised an option to leave when talks on a new deal broke down, and joined the Chicago Cubs.
"The voice is obviously probably going to change a little bit, but the players and the personnel, and the culture, what they created, that is something that I'm extremely fortunate to be a part of and join in on," Cash said.
The new manager inherits a roster driven by one of the best pitching staffs in the American League.
Starter Alex Cobb received a phone call Friday from Cash and was impressed with his new manager's dedication.
"I like him," Cobb said, according to the Tampa Bay Times. "He seems like he's got the type of energy that we're looking for. The short conversation I had with him, it seemed like he was extremely excited just to have the opportunity to be the manager, obviously, but you could just hear the passion he had for the upcoming job and the task at hand. It just felt like the right fit."
Most of Cash's coaching staff will be comprised of holdovers from Maddon's reign.
"When it got down to it, the security of our situation with our staff in place, and the clubhouse culture that we have, gave us more comfort," Silverman said.
"But, you look at Kevin, his baseball age is much older than his 37 years on this planet," Silverman added. "He's been a student of the game, and that transition to manager is one we think will be a relatively (smooth) one, one made easier by the environment that we already have here."
Tampa Bay star Evan Longoria said he was "really excited" by the hire.
"I'm really excited about the new direction," the third baseman told the Times via text. "Kevin brings experience as a player at the major league level, which excites me, along with a fresh attitude that I feel will translate into making our already great clubhouse even better."
Maddon opted out of his contract on Oct. 24 and was hired to manage the Cubs.
Rays principal owner Stuart Sternberg said Cash's "energy and dynamic personality will fit seamlessly with our clubhouse."
Wakamatsu was the only candidate among the finalists with prior managerial experience at any level, having gone 127-147 in one-plus season as the Mariners' skipper in 2009 and 2010.
Veteran outfielder Raul Ibanez, still an active player after spending his 19th big-league season with Kansas City and the Los Angeles Angels, was the third finalist. He withdrew his name from consideration this week.
Before joining the Indians in 2013, Cash spent one season as a major league advance scout for the Blue Jays.
Silverman said it was a tough decision between Cash and Wakamatsu, who has spent 10 seasons as a bench coach with the Royals, Blue Jays, Oakland Athletics and Rangers.
Wakamatsu took over a team that lost 101 games and led Seattle to an 85-77 record in 2009. He fired in August of the following season, when the Mariners stumbled to a 42-70 start.
Former Rays bench coach Dave Martinez, one-time Indians manager Manny Acta, Hall of Famer Barry Larkin, San Francisco Giants bench coach Ron Wotus, Rays minor league manager Charlie Montoyo and ex-major league players Craig Counsell and Doug Glanville rounded out a list 10 initial candidates.
Martinez has since joined Maddon's staff in Chicago.
The Associated Press contributed to this report.