The news comes after the midfielder was released by Hearts last month.
The 27-year-old - whose first match will mark his 150th appearance for the Ayshire club - was one of the high-profile players allowed to leave following the arrival of Ann Budge and Craig Levein at Tynecastle. Hamill spent three years at Hearts, a spell which culminated in the club's relegation to the SPFL Championship.
He will remain in the top flight with Kilmarnock, though. A statement read: "We are delighted to confirm that Jamie will be returning."