Stephen McNamara joined the Irish airline this week, moving from Dublin-based PR and public affairs shop MRPA Kinman, where he was employed as an account manager.
McNamara has been brought on board at Ryanair to replace Sherrard, who left the company in May (PRWeek, 1 May).
One of McNamara's new challenges will be to manage the fallout from comments made by the airline's famously outspoken CEO Michael O'Leary.
The company is also renowned for its PR stunts and sideswipes directed at the rest of the airline industry.
McNamara's previous accounts included working with clients such as Irish Life. While at MRPA Kinman, he reported to managing director Ray Gordon.
Former comms boss Sherrard has gone to work for the Football Association of Ireland as director of communications.
He is responsible for the FAI's corporate communications activity.