Temple, who was previously a creative director at the agency working on Nokia, joins Nathan Cooper, who was hired from Poke London to the same role a year ago. Both will lead the agency's creative output, but Temple will focus on core skills that include web, mobile, outdoor and retail.
He will report to Jim Moffatt, the recently appointed managing director.
Temple has been at the agency for two years. Most recently, he led the team on "Urbanista Diaries", the global online campaign for the N82 phone. Before that, he was a design director at Electronic Ink in the US and previously worked with IBM in Toronto.
Chris Colborn, R/GA's executive vice-president and chief creative officer, said: "James has been one of the strongest creative forces leading the agency forward. He has an impressive track record and a strong vision."
The London agency's clients include John Lewis, SC Johnson and Nokia.