The 32-year-old, who was released by the Buddies last month, has spent the past three years north of the border.
However, he is now relishing the opportunity to continue his career, which has featured spells at Swindon Town, Ipswich Town, Luton Town and Walsall, back in England.
He told reporters: "Exeter were looking to bring in a front player and fortunately after having a meeting with the manager and a really good chat, I've been down to have a look at the place and I'm really delighted to have signed.
"I know that Exeter have got a tradition of playing good football and the manager has obviously got a great reputation, so it was a no-brainer really.
"I'm just delighted to get another opportunity down here to play football and hopefully be part of a successful team."
Parkin scored just two goals in 27 Scottish Premier League appearances last season.