Fotuaika was poised to make his NRL debut this season after helping the Tigers under 20s side win Toyota Cup title last year.
The 20-year-old appeared in a number of trial matches for the senior side in the past month.
Gisborne-born, Fotuaika moved to Australia and attended Keebra Park High on the Gold Coast, the same school as Benji Marshall.
A NSW police spokesperson said: "At about 6.50pm (AET) Police from Holroyd area command were called to a town house in Merrylands.
"Afterwards a 20-year-old man was found deceased inside the premises.
"The death is not being treated as suspicious. A report will be prepared for the coroner."
The Wests Tigers official Facebook site posted: "Thoughts and prayers go out to the wests tigers very own moses Fotuaika and his family during this very difficult time may god help them and watch over them !!"
