Finn, 35, is beginning his second spell with the club after playing for them from 2006-2009. He left the playing squad at Wakefield – where he is still a member of the backroom staff – at the end of last season to join Newcastle Thunder, but has returned to West Yorkshire after just three games for the north east club.
Finn, who has also played for Halifax, Featherstone Rovers and Widnes Vikings, has signed until the end of 2020. Travelling to Newcastle for training and matches had taken its toll and the ex-Ireland international said: “I’m really disappointed to have made this decision and leave the club after such a short time.
It was obviously never the plan, but circumstances change and I’ve made a decision within that.
“I’ve left a great club with ambition that is doing a great deal of good for our game with some fantastic people who work very hard.
“I’m gutted to have had to make this call and hope they and Thunder kick on and achieve what they’ve set out to do.”
Rams chairman Mark Sawyer said: “We are delighted to have Liam Finn back at the club and we would like to place on record our thanks to Newcastle Thunder and chairman Mick Hogan for his dealing in the transfer.”
Hogan added: “We’re naturally disappointed that Liam is leaving the club.
“He has been all we expected him to be when he signed in the winter and has been an experienced voice and influence within the squad.
“Whilst it is a shame, we understand the strains that he has been under with the travelling from Wakefield to Newcastle and respect his desire to play somewhere closer to his family.
“We’d like to thank him for all his efforts with Thunder over the last four months and wish him well for the rest of the Betfred Championship season with Dewsbury.”
Meanwhile, former Rams hooker Dom Speakman has signed for Widnes Vikings after a spell as a trialist in pre-season.
Widnes have also signed ex-Castleford Tigers back-rower Luis Johnson on loan from Warrington Wolves.
Hooker Liam Hood, who began his career at Leeds Rhinos, has returned to Leigh Centurions after leaving Widnes.