Irish mobile maritime communications company Blue Ocean Wireless has teamed up with picocell developer ip.access to develop the system.
For crews, separated from their families for months on end, the ability to be able to make and receive calls from their mobiles will be a big boon.
Previously merchant ship crews had to rely on expensive satellite phones.
The new system will also rely on satellite communication. A picocell - a small base station that extends mobile coverage - will be installed in accommodation areas of the ship.
Connected to a remote gateway, it will convert a mobile call into a narrowband IP signal for transmission over the satellite network.
Picocells are increasingly being used to extend mobile coverage to places where exterior signals cannot penetrate, such as office buildings, ships and aircraft.
UK-based ip.access has already done a series of deals which have put picocells onboard ferries and cruiseliners.
Extending the service to merchant ships will "bring the benefits of mobile cellular communication to seafarers who spend so much time away from friends and family," said ip.access chief executive Stephen Mallinson.
Typically such picocells are used by mobile operators on 'terra firma" to boost indoor network coverage in buildings and for business customers in offices.
But anywhere where traditional GSM coverage is difficult could potentially be a candidate for using picocells.
British Airways has announced that it will be using picocells on planes from the autumn.
It will enable air passengers to send and receive text messages and access the internet using a smartphone or GSM-enabled laptop but BA is stopping short of allowing voice calls.