The ABC drama centres on Marta Walraven (Radha Mitchell), whose gangster husband is killed by a rival group, prompting her to work with the FBI to expose the criminals behind the murder.
Former ER series regular Visnjic will take on the role of the mafia mob boss responsible for the hit placed on Walraven's husband, reports Deadline.
Red Widow will serve as a midseason replacement to premiere in late 2012.
Visnjic joins recently cast actors Lara Pulver (Sherlock, Spooks) and Southlands' Clifton Collins Jr in the cast.
Wil Traval, Lee Tergesen, Rade Sherbedzija, Luke Goss, Jaime Ray Newman and Mido Hamada will also star in Red Widow.
Watch the trailer for Red Widow below: