The agency won a competitive three-way pitch and will be responsible for communicating the NACM's key messages, industry news and campaigns relating to fairer duties.
Richard Jukes, Grayling’s public affairs managing director, said the agency would work to ensure the duty rates are maintained and that the industry is better understood by stakeholders and politicians.
He added: "We are delighted to be working with NACM and promoting the interests of the cider and perry industry in the UK, through a joint public relations and public affairs approach."
Bob Price, director and policy adviser at NACM, said: "Grayling is joining us at a very exciting time and we look forward to its support across public relations and public affairs to help communicate the voice of our industry."
The NACM works to protect the interest of larger producers and hundreds of small-scale cider makers in the UK.