Infratil-owned NZ Bus has sold Auckland-based Fullers Ferries for $40 million to Souter Holdings.
NZ Bus runs bus services in Auckland, Wellington and Whangarei.
Its chief executive officer, Bruce Emson, says the money will be used to build the operation and get more people onto its buses.
Mr Emson would not be drawn on any further sales, though the company is considering selling some of its bus depots, which analysts say could give it another $20 million.
Infratil says it has sold more than $100 million of assets in the current financial year, including a $60 million gain from the right to make the City of Luebeck buy Infratil's 90% stake in the German city's airport later in the year.