She'll be joined by Joe Spano, who plays her character's other ex-husband (and Gibbs' best friend), FBI Special Agent Tobias Fornell.
"Imagine being the ex-wife of both Gibbs and FBI Agent Fornell," says 'NCIS' executive producer Gary Glasberg.
"Melinda McGraw brings enormous heart, humor, bite and edge to a character we've known about for years, but haven't spent much time with. This is gonna be fun!"
Diane split from both men acrimoniously and cleaned out their bank accounts when she left, so we can expect fireworks when she reappears. The triumvirate will reportedly be reunited after Diane's most recent husband gets caught up in a joint NCIS--FBI investigation.
Originally a spin-off from 'JAG,' 'NCIS' follows a fictional team of agents from the Naval Criminal Investigative Service as they investigate criminal cases involving the US Navy and Marine Corps. Ratings have consistently climbed since the show debuted on CBS in 2003, and it reached the Top Ten in its fifth season. Last season it became the most-watched scripted show on US TV.
Season 9 of the long-running procedural got off to a strong start last week, with the first two episodes pulling in around 19 million viewers each.
'NCIS' Season 9 airs Tuesdays, 8PM ET on CBS.