The agency will start work on the business in August, focusing on IHG's core brands, which include Holiday Inn, Holiday Inn Express and Crowne Plaza.
The McCann pitch was led by a team from McCann Erickson Communications House, its 300 strong integrated agency based in Prestbury, Cheshire.
The account will be led and managed by MECH who will access local agency resources in key IHG markets and a support team in its London office.
William Morris, IHG's senior vice president, Sales & Marketing, EMEA, said: "IHG has some of the World's greatest hotel brands -- the McCann Erickson team demonstrated a clear understanding of our brands and offered strong creative execution that will help us deliver our aggressive targets for this year and beyond."
Brett Gosper, McCann Erickson EMEA president, said: "This is a significant win for us and it's exciting to be partnering with IHG at this time as they continue to build on their worldwide growth and success."
Media planning and buying, handled by Carat, is unaffected by the appointment.
IHG also recently appointed Henry's House as its lead UK PR agency.