Evans (pictured) has served as a special adviser to three Conservative governments since 2016, under David Cameron, Theresa May and Boris Johnson.
In a newly-created role in public and political affairs, he will advise on politics and strategy in London and across H+K’s global network.
During his time at Whitehall, Evans focused on energy, transport and infrastructure projects.
H+K said he was an early champion of the Prime Minister’s ‘levelling up’ agenda and worked with the Secretary of State for Wales on the devolution agenda.
Prior to government, Evans founded his own marketing and communications agency and was a PR manager for a Fortune 500 company.
"Geraint’s reputation and knowledge of the inner workings of Government is a great addition to H+K," H+K UK CEO Simon Whitehead said.
"Modern day public and political affairs is an indiscernible part of multichannel campaigning for reputation and brand management; we continue to win fascinating and complex new mandates in this discipline across our industry sector teams."
Evans added: "Having been at the centre of British politics during a historic period, it is clear that industry and Government can and must work more smartly together as we move to grab opportunities beyond EU exit."