Newman, who previously starred as Kat Gardener in Eastwick, will have a major arc in season two of the Lifetime comedy, Entertainment Weekly says.
She is expected to play a lawyer with a "killer instinct" who works for a rival firm to Jane's (Brooke Elliot).
Meanwhile, Gilmore Girls star Emily Kuroda has signed up to play the mother of Teri (Margaret Cho).
Robin Givens will also join the show as a cosmetics lab executive who accuses one of Jane's clients of wrongdoing.
The second season of Drop Dead Diva is scheduled to premiere on June 6.