Kiwibank is one of five banks, including Westpac, which have been awarded a smaller contract to provide payment services.
Mr English said the new deals would deliver savings of more than $120 million over the life of the various contracts.
"The new contracts provide government agencies with a choice of providers that have undergone a rigorous procurement process, and support the implementation of innovative banking solutions for all New Zealanders," Mr English said in a statement.
As well as the main Westpac contract, the Government has also appointed a selection of banks to provide other services, including:
• Foreign exchange transactions - ANZ, ASB, Bank of New Zealand, Citibank and Westpac (three year initial term).
• Payment services - ANZ, ASB, BNZ, Kiwibank, and Westpac (three year initial term).
• Card services - ASB, BNZ, Citibank and Westpac (three year initial term).
The 35 core government agencies are required to use Westpac. Other agencies can use another provider for their transactional banking.