AC Milan have dismissed Mihajlovic and promoted youth-team coach Brocchi as his replacement until the end of the season.
Mihajlovic left his role as Sampdoria coach and replaced Filippo Inzaghi at San Siro last June, but he leaves the club 10 months into his tenure, despite sitting sixth in Serie A and having navigated the team to the Coppa Italia final.
Saturday's 2-1 defeat to league leaders Juventus proved the final straw, extending Milan's winless run to five matches and leaving them 15 points adrift of third-placed Roma in the final Champions League qualifying berth.
A statement on the club's official website read: "Sinisa Mihajlovic has been relieved of his role as AC Milan coach.
"The club would like to thank Mihajlovic for the dedication and hard work carried out this season."
Mihajlovic's replacement until the end of the campaign has been confirmed as Brocchi, who had two separate spells as a Rossoneri player from 1994-1998 and 2001-2008 and had been coaching the youth team since 2014.
Brocchi took over that position from Inzaghi, but will look to avoid his predecessor's fate when in charge of the first team.
The 40-year-old becomes the fifth coach to take charge of Milan in the past three seasons.
