Burns has been at Fallon since the agency was founded in 1997. She will head the branded content division at the production company and will produce for the former Fallon executive creative director, Andy McLeod, who joins the company in January.
Burns said: "Rattling Stick offers a talent base experienced in creating quality content. It's a perfect environment to nurture the new opportunities in branded content."
Ledwidge added: "We're delighted Kirsty has agreed to join. Her experience and enthusiasm will be invaluable."
Kleinman and Ledwidge launched Rattling Stick in April. Both directors have a host of award-winning commercials on their reels. Kleinman founded Kleinman Productions with his producer, Johnnie Frankel. Ledwidge formed Small Family Business with his producer, Sally Humphries, in September 2003.