The 21,900-gt Stena Feronia (built 1997) will replace the 1,350-lane-metre Santa Regina (built 1985) in June.
The vessel was running between Sweden and Germany until recently. No price has been revealed.
Strait Shipping's managing director, Sheryl Ellison, told the Dominion Post that Stena Feronia would capable of carrying 60 trucks, 150 cars and more than 500 passengers.
"The Stena Feronia's overall condition, layout for both freight and passengers and fuel efficiency made her the pick of the bunch amongst a number of other vessels researched.
