By the sixth round, Ngabu was getting too much for Masson, sending him to the canvas.
Masson got on his feet at the count of eight, but referee Will Soulos decided enough was enough, with Ngabu winning by TKO.
It is unknown what is next for Masson, but he will need to take some time over the next few months for the cut to heal.
On the undercard, Auckland boxer Benjamin Kelleher lost thanks to a second-round KO from Australian Luke Modini and so lost his Australian National title, also in his first defence.
Kelleher said at the end of the fight that if this was not the last fight, his career would soon be coming to a close.
When Masson does eventually return to boxing, Modini will be an excellent boxer to compete against. This would be a good fight for a major regional title to cement the winner in the top 15 rankings.
If you want to see the IBO World Cruiserweight title fight between Floyd Masson and Yve Ngabu, promoter Ace Boxing Group have released footage of the event on YouTube.