The actress will play Nikki Kirkbright, billed as “a Cheshire housewife that seems to have it all - money, big house and big hair. But something isn’t quite right”.
Viewers will see Robert Bathurst’s character David Marsden meet her through his career in finance, and the duo will soon build a bond.
Sharing her joy at joining the cast, Siobhan said: “I’m incredibly happy to be involved in ‘Cold Feet’ as I’ve always been a fan.
“It’s an absolute joy to be part of such a iconic series. Working with Robert and the rest of the cast has been a great pleasure.”
TV fans might recognise Siobhan from ‘Happy Valley’, ‘Downton Abbey’ and ‘Benidorm’.
The seventh series of ‘Cold Feet’ will arrive on our screens later this year and pick up 10 months on from the last series finale, which saw Adam Williams (James Nesbitt) finally confess his feelings for landlady Tina Reynolds (Leanne Best) at his fake 50th birthday party.