Deadline reports that Ticotin will be a series regular in the new spinoff.
She is expected to replace Wanda De Jesus, who left the show earlier this month after producers decided to "take [her] role in a different direction".
Ticotin will star as the new lieutenant leading the LAPD Robbery Homicide Division. De Jesus reportedly filmed scenes for the first two episodes, but Ticotin is expected to reshoot them next week.
Law & Order: LA will premiere on September 29 on NBC.