The show is to return with a run of fresh episodes Sept. 21.
Kelton will play the "spirited and fierce" Jordan McKee, a waitress and influential member of a mysterious organization of "troubled" people whose identity is known by the distinctive tattoo marking its members, Syfy said.
Missick will play Tommy Bowen, "a street-smart Boston detective" who comes to Haven investigating a suspected serial killer case.
Based on Stephen King's novella "The Colorado Kid," "Haven" follows former FBI agent Audrey Parker, who becomes a police detective in the small town of Haven, Maine. She soon discovers the hamlet's many secrets, which also hold the key to unlocking the mysteries of her lost past.
Emily Rose plays Audrey.