The move completes the Starcom UK chief executive Linda Smith's new line-up at the Publicis-owned agency.
Smith said: "Parkinson is one of the most energetic and dynamic people I have ever met. She brings a combination of strategic thinking and leadership skills to the group, coupled with an unrelenting passion for life. There's a real feeling of change in the air at Starcom."
Parkinson, who starts in January, will be responsible for Starcom's core product offering, strategic research and insight, marketing and new business. She has also been handed a seat on the Starcom management board.
Parkinson, who quit Nylon a year ago and has since been working on a freelance basis, joined the WPP-owned communications planning business as a founding partner in 2004.
The agency was formed as a joint venture between the Young & Rubicam Brands and Mediaedge:cia in a bid to challenge the success of start-ups such as Naked.
Before this, Parkinson helped to form the online communications agency OnlineVisibility, following six years as the UK chief executive of Universal McCann, which she joined in 1995.
Other candidates for the strategic planning role included former managing partner of OMD, Mark Palmer (Campaign, 1 September). Talks, however, broke down and Palmer will continue to run Maverick Planet.