Filming has started in Dublin on the show's second run, which will feature the return of Matthew MacFadyen, Jerome Flynn and Adam Rothenberg as crime-solving trio Reid, Drake and Jackson.
Costabile joins as Daniel Judge, the older brother of Jackson (Rothenberg), and will appear in the two-part finale.
Molony joins as new H Division constable Albert Flight, while Mawle is cast as the corrupt Inspector Jedidiah Shine. Newcomer Leanne Best will appear as Jane Cobden, the first woman elected to the London County Council.
Meanwhile, Paul Kaye (Dennis Pennis, Game of Thrones) is among the guest stars in series two, alongside Gina Bellman (Coupling), Neve McIntosh (Doctor Who and James Wilby (Maurice).
Based around the East End of London, the second series will move the show forward to 1890. Series two will launch in the UK in early 2014.
Speaking about series two, MacFadyen said: "It's fantastic to be reunited with much of the wonderful cast and crew from last year. Also to be reunited with my bowler hat - I'd missed it.
"The show's creator Richard Warlow has given us wonderful, strange and unsettling episodes, teeming with the fierce and fragile life of Victorian Whitechapel."
Ripper Street's first series launched with 7.89m viewers in December 2012. It airs in the US on BBC America.