AgustaWestland said the aircraft will be used to perform fire fighting, emergency medical service, air rescue and transport missions.
The helicopter is to be delivered late this year and will enter operational service next spring.
This AW139 sale follows an order for the same helicopter type by the Saitama Prefecture in January.
"We are proud to provide Japan with an additional AW139 helicopter to support its range of demanding emergency mission requirements," said AgustaWestland's Head of Region, NE Asia, Andrew Symonds. "Thirty AW139s have been ordered by customers in Japan so far, confirming its position as the most advanced mission capable helicopter available today in the medium twin class."
Advanced avionics selected with the helicopter include a satellite-based augmentation system-capable GPS, an enhanced vision system, enhanced ground proximity warning system and a traffic collision avoidance system.
This latest contract further strengthens the presence of the AW139 in the Japanese helicopter market, where 30 have been ordered by several customers such the Tokyo Metropolitan Police Department, Japan coast guard and the National Police Agency.