Litzow, who left Grass Roots in September 2011, joined George P Johnson in January and will work across the agency's technology accounts, which include Cisco and IBM.
Litzow said: "The way in which GPJ operates is unique in our industry. Its strategic disposition and approach is something that really drew me here and fits into my philosophy built over a 25-year career."
Before joining Grass Roots in January 2011, Litzow spent over a year taking an MBA at Henley Business School. She has also worked in-house as a vice-president of global events at computer software firm SAP.