The actors will both portray detectives on the NBC drama, taking up their new roles next season.
"Kelli and Danny are two great actors who will join a proven cast headed by Mariska Hargitay as this exceptional series heads into a very promising 13th season," said NBC Entertainment chairman Robert Greenblatt in a statement.
Creator Dick Wolf added: "I'm very pleased that we have two amazing actors joining the cast. I know this combination will give us the opportunity to explore the world of SVU with new eyes."
Cold Case star Pino's role will essentially replace the one currently held by Christopher Meloni, who announced that he would not return for Law & Order: SVU's next season.
Giddish played as Annie Frost in the short-lived Chase and recently made a guest appearance as Sophia Russo in The Good Wife.
SVU star Mariska Hargitay will also leave the series after season thirteen and will take a reduced role for her final year.
True Blood actor Kevin Alejandro was recently rumoured to be in the running to join the cast.