Guardiola managed Alaba at Bayern between 2013 and 2016, winning the Bundesliga title in all three campaigns he was in charge.
Prior to his time in Germany, Guardiola presided over a wildly successful Barcelona side that won more than a dozen trophies in four years.
In addition to domestic success in Germany, the Austrian defender says Guardiola helped instill a new style of football at Bayern.
"He meant a lot to me," Alaba said. "I learned a lot from working with him. I knew that I could make a lot of decisions [on the pitch] and I guess he’s one of the best coaches in the world, if not the best."
"He brought a new style of football – not only to our team, but to the world. We improved. We learned a lot about football and the way we played.
"When we won the championship ... the style of football that we played was great."
Guardiola has gone on to Manchester City, where he sealed a runaway Premier League title last season.
Despite continuing domestic silverware, the Spaniard hasn't achieved Champions League success since his time at Barcelona.
Alaba, though, believes that City could have got more out of a surprising Champions League quarter-final exit to Liverpool last season.
"They won the championship in England in a really good way," the 26-year-old said.
"He’s doing a great job. He was unlucky in that Champions League [quarter]-final against Liverpool."
Alaba was speaking ahead of Bayern Munich's Audi Summer Tour of the USA. Bayern will be playing two games are part of the International Champions Cup:
July 25th in Philadelphia vs Juventus
July 28th in Miami vs Manchester City
For tickets, visit https://fcbayern.com/us/us-tour