Alison Clarke replaces Tobin, joining from parent company Huntsworth Group where she is business development director.
Clarke said: ‘It's an exciting time to return to consultancy management as Grayling is now firmly established in the UK with a powerful international network. I'm looking forward to working with people and clients I have known within the group for many years.’
Tobin, who has been with the consultancy for 17 years, said this was one of the hardest decisions she has ever made.
‘I'm passionate about this company, its people and clients but after 17 years it's time to take a well-earned break and see more of my family,’ she said.
Clarke was formerly CEO of Weber Shandwick Asia Pacific, having previously run Shandwick Welbeck in London.
Grayling International CEO Michael Murphy paid tribute to Tobin: ‘Loretta has made a huge contribution to our business, not only in the UK but internationally and will be missed by staff and clients alike.’