The French club has finally confirmed they have secured the full-back – the world’s costliest player – on a three-year deal starting in 2019.
Wigan, though, were unhappy about Catalans’ approach for Tomkins, saying they made it before the May 1 deadline.
Still, the 29-year-old – offered reduced terms by Wigan – will leave his hometown club for a move overseas for a second time having initially joined New Zealand Warriors in 2013.
It clears the way for Wigan to announce they have signed former Leeds Rhinos, Castleford Tigers and England full-back Zak Hardaker for 2019 once his drugs ban expires.
“After speaking with Catalans it was clear the club has big ambitions and I want to be part of that,” said Tomkins, although Dragons currently sit bottom of Super League.
“I have worked with Steve for five years at international level and I am looking forward to working with him again.”
Wakefield Trinity prop Jordan Baldwinson, 23, has joined Championship Leigh Centurions on a one-month loan.
He can debut at former club Featherstone Rovers on Saturday.
Hull KR’s Danny Tickle received a Grade A penalty notice for the punching offence that saw him red-carded against Wigan, meaning he is free to face Hull FC in the derby at Magic Weekend.
Hull’s Challenge Cup quarter-final at St Helens will be televised by the BBC on Sunday, June 3 (3.30pm) with Warrington v Wigan on the previous day (2.30pm).
Sky Sports broadcast Leeds Rhinos v Leigh Centurions (Friday, June 1, 7.35pm) and Huddersfield Giants v Catalans (Thursday, May 31, 7.35pm).