Turner revealed her and husband Justin Saliman's happy news during an interview with NBC San Diego at Comic-Con over the weekend.
The actress commented that Grimm's cast and crew have been nothing but accommodating since she became pregnant.
"It has been hysterical [to work while pregnant]. But thankfully the crew has been very flexible with my current situation," Turner said.
Turner and Saliman welcomed their 2-year-old daughter Stella Jean in 2010.
The actress was named a series regular on Grimm in April.
Grimm premieres its new season on August 13 on NBC.
Watch a Grimm preview below: