The L Word actress will play Lainey, a "sexy, wry-humoured" but widowed hair salon owner whose cop husband lost his life on the job, according to Deadline.
The drama stars John Corbett as Denny Brennan, a detective who becomes a surrogate husband, lover and father to the families of his three past partners - all of whom died in the line of duty.
Elyes Gabel has been cast as Denny's current partner, while Eric La Salle will guest-star in the pilot as Lieutenant Lutrell.
Beals - well-known for playing Bette Porter in The L Word - recently played Teresa Colvin in the short-lived series The Chicago Code.
She has also had roles in Lie to Me and the film The Book of Eli.
Beals claimed last month that she was "not interested" in any of the pilot scripts that she read.
Watch a promo of 2011's The Chicago Code below: