The 80-year old designer, known for his clean cut and elegant collections, was joined by celebrities such as Leonardo Di Caprio, Cate Blanchett, Hilary Swank and Tina Turner for the bash in Milan on Friday, headquarters to his fashion empire.
Nicknamed King Giorgio, the designer, who once worked as a window dresser, is known for being hands-on in creating one of the most recognised fashion brands in the world.
"There have been many moments, from the beginning until today," Armani told reporters upon arrival at the gala on Thursday evening. "Maybe my most emotional moment was when I saw my cover on 'Time'," he added referring to the magazine.
Armani, who designs both couture and ready-to-wear, has dressed celebrities, royals as well as sportsmen. Stars such as Beyonce, David Beckham and Megan Fox have modelled his perfumes or underwear.
"Madison Avenue in 1985, I think it was, so not very long after he came to our country and I have a closetful still of those beautiful suits, those classic suits, and I still wear them," actress Glenn Close said of when she bought her first Armani piece.
"James Bond" actor Pierce Brosnan paid tribute to the stylist, calling him "a mighty man" while Italian actress Sophia Loren simply said the designer "is my friend".
For the anniversary, Armani has converted a 1950s building that once stored cereals for a new exhibition dedicated of his designs.
The event took place ahead of the Friday opening of the Milan Expo, of which Armani is a special ambassador for fashion.
Officials are counting on some 20 million people visiting the six month exhibition of worldwide products and technologies.