The Rossoneri have had a terrible start to the new season, losing both the opening two home games and drawing their first Champions League group stage game against Anderlecht.
Pressure had been building on Galliani, but the former Italian prime minister has said that there is no truth in rumours that his head is on the chopping block.
"I take this opportunity to reiterate my total faith in Adriano Galliani," said Berlusconi.
"There have been some articles relating to Milan and its structure. These articles are devoid of any truth.
"He is one of the greatest men in the game and has been my friend for 30 years. I have unconditional professional respect for him."
Galliani took up his position in 1986.