The defender has signed a three-and-a-half-year contract with the Italian giants in an agreement that could also see midfielder Rodney Strasser move to Parma.
"I am delighted and honored to be in a so important club and I will do everything to make my contribution," Zaccardo told the Milan Channel.
"I'm proud that Milan has interested in me. At age 31 I am here, after so many Serie A matches and I will give everything".
The transfer has fuelled rumours that Ignazio Abate could now leave Milan in favour of a move to Russian outfit Zenit St Petersburg.