H&K will replace consumer shop Henry's House following a global review of IHG's comms support.
In the US, Weber Shandwick has held on to its account with IHG and the firm will continue to use H&K in China.
IHG's global PR spend is thought to be around US$2m annually and this is set to rise as PR becomes increasingly central to the group's marketing strategy.
'We are investing more in PR and comms than we have done previously,' said Leslie McGibbon, IHG's senior vice-president, global corporate affairs.
'We have deflected some of the budget that has previously gone into traditional marketing into PR to get a bigger bang for our buck with consumers.'
H&K's UK brief will be expanded from the work that Henry's House did to include public affairs and corporate work as needed and a specific focus on digital PR.
McGibbon said: 'The majority of our customers book hotel rooms online so social media and new media will be central to our PR strategy moving forward.'
McGibbon also said H&K's ability to offer digital, corporate and lobbying expertise under one roof was a key factor behind its appointment.
IHG has more than 620,000 rooms in more than 4,200 hotels across nearly 100 countries and leading brands include InterContinental, Crowne Plaza, Hotel Indigo and Holiday Inn.
One of H&K's first tasks will be supporting the relaunch of Holiday Inn over the next six months, as part of a £600m global programme.
[XX] Hole in one Ryder Cup Europe has appointed KTB PR to handle consumer PR for next year's competition. KTB has been briefed to raise awareness of the 2010 Ryder Cup among key audiences throughout Europe, as well as generating interest in the UK.