The show was originally cancelled by ITV but was later revived when the channel teamed up with UKTV, BBC America and German broadcaster ProSieben.
Hannah Spearritt, Andrew Lee-Potts, Ben Miller, Jason Flemyng, Lucy Brown and Ben Mansfield have all returned to the show, while new cast members include Alexander Siddig, Ciarán McMenamin, Ruth Bradley, Jonathan Byrne, Anton Lesser and Ruth Kearney.
The programme's executive producer Tim Haines said: "The cast and crew have been brilliant and they have put in a huge effort over the past four months to deliver some amazing work. We have also been very lucky in that Dublin has afforded us some fantastic new locations and the fact that we've filmed in HD for the first time means that the production values are higher than ever.
"The rough cuts I've seen are very exciting and I think we are going to deliver a show that will really please and delight the fans."
The fourth series of Primeval will premiere on ITV1 next year before being broadcast on Watch. The cast are currently filming the fifth series.