Moody's reaffirmed the top-shelf rating because of the state's "diverse and robust economy" on Wednesday, adding "strong" government performance also contributed to lending confidence.
The high credit rating signals the government is unlikely to default on any loan, meaning money can be borrowed at lower interest rates.
Moody's decision flies in the face of the government's pre-budget predictions, where it lamented the likely impact of a small-than-expected slice of the national GST pie.
Treasurer Daniel Mookhey repeatedly said the carve-up, which left NSW $11.9 billion worse off than projected over four years, would tank the state's remaining AAA ratings.
NSW Treasurer Daniel Mookhey says the rating confirms the work being done by the government. (Dean Lewins/AAP PHOTOS)
Fitch is yet to downgrade its AAA grade for NSW debt, while the other major agency, S&P, has maintained a AA-plus rating.
Moody's said GST funding remained a "strong and fairly predictable source of revenue", although it warned if state debt continued to increase a future downgrade could be on the cards.
"Pressure could stem from a potential slowdown in economic activity or a slow down in revenue growth, for example from weaker housing market activity, negatively impacting the primary operating balance and debt affordability," it said.
"Likewise, if NSW's policy response proves to be less effective than what we currently assume and results in a larger and longer-lasting increase in debt, then this would denote an erosion of the state's governance strength."
The state's gross debt is expected to hit nearly $200 billion within four years, according to forecasts in the June budget.
Mr Mookhey, who had labelled the GST carve-up a "rip-off", said the rating affirmation was a tick in his government's box.
"This determination is an acknowledgement of the difficult work that has been done to wrangle the state's debt back under control," he said.
"We accept that stress remains on the Triple-A rating and Moody's provides a sobering reminder of the work still ahead."
In March, Premier Chris Minns labelled the federal government's GST distribution "unfair" after his state received its largest-ever single-year cut.
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