Actor and musician Foxx teased the announcement on social media, releasing a phone call between himself and Diaz.
It comes eight years after the pair appeared together in what became Diaz's last film - a 2014 remake of Annie, in which she played Miss Hannigan.
Diaz, 49, said she was "so anxious" but "excited" about returning.
During the same phone call, Foxx, who won an Oscar for his 2004 portrayal of US soul singer Ray Charles, connected Diaz with the Super Bowl-winning Tom Brady in order to offer some advice about launching a big-time comeback.
