Osbourne, the 54-year-old wife/manager of rocker Ozzy Osbourne, will make her debut May 29, when the reality competition returns for its second season, NBC announced Thursday.
"On this show, it just had to be Sharon Osbourne," said executive producer Simon Cowell in a statement.
Osbourne will join returning judges David Hasselhoff and British media figure Piers Morgan. Jerry Springer is the new host of the $1 million-prize contest.
She starred with her family in MTV's reality series "The Osbournes."
Brandy, 28, was involved in a Los Angeles freeway crash last December that killed a 38-year-old woman. Two wrongful death lawsuits have been filed against the actress-singer on behalf of the woman's family.
"Brandy has enjoyed her association with the program. However, she felt she couldn't give the new season the attention and commitment it deserved," said a statement by Brandy's spokesman, Courtney Barnes, which was released by NBC.
NBC is owned by the General Electric Co.