He assumes the newly-created position from his role at tech agency Chameleon. He has also previously worked at consumer shop Lexis.
Hehir has worked on consumer campaigns for brands including Discovery Channel Europe, Crussh, Guinness Barclaycard and the Rugby Football Union.
He will also strengthen Pegasus PR's digital offer with his experience working for business social network LinkedIn.
The move to further expand the senior team comes as the agency continues to experience steady growth, increasing its income by 39per cent last year to £1.4m.
The agency is currently on track for 40 per cent growth this year.