Berkeley PR said it will provide strategic direction on corporate communications and look to raise the profile of products such as AlphaElectric, which helps businesses and their drivers switch on to electric vehicles.
David Jones, communications manager at Alphabet, said: "Our aim is to lead the way in our industry and set the agenda in the UK for business mobility. Our focus on innovation means there is always an exciting new development on the horizon. Berkeley PR had strong credentials and a clear vision for how they would get us where we want to be."
Alphabet has doubled in size since 2011 and is now the third biggest player in the UK fleet leasing industry. Founded in 1997, it operates across 18 markets.