Fitch Ratings says Kiwibank has a stable outlook and is improving its profitability and balance sheet structures.
In May, Standard and Poor's downgraded the bank's outlook to negative, citing risks such as increasing house prices which could affect the credit standing of the bank and its parent New Zealand Post.
However, both ratings agencies see the fact that the bank is Government-backed as a safety net.
Andrea Jaehne, a director at Fitch's financial institutions team based in Sydney, says the agency has Kiwibank's long-term issuer default rating as AA with a stable outlook.
Ms Jaehne says the bank is improving its capital and its profitability. However, it has a viability rating of BBB minus.
"From a viability rating perspective, I think they are on the lowest category for an investment grade but we see the bank is on an improving trend. Nevertheless, its IDR - its main rating - is really driven by support from the Government."