TV Guide says that the Numb3rs star has signed up to play Lt. Jason Paul Dean, a mercenary linked to the private military company run by Col. Merton Bell (Robert Patrick).
Lt. Dean is said to be a dangerous former Army Ranger who was highly decorated until he received a dishonourable discharge.
His arrival is thought to be worrying for Gibbs (Mark Harmon), who arrested Bell earlier this season.
Bruno's character will first appear in the penultimate episode of the season but will also star in the finale, when Gibbs is forced to make a difficult decision to save his team.
NCIS returns for the first of five new episodes on Tuesday at 8/7c. The season finale is scheduled to air Tuesday, May 25 at 8/7c.