Fears for missing Kiwi

New South Wales police say they hold "grave concerns" for a New Zealander missing since last month.

Oliver Sims, 26, was last seen on September 18 at a university in Wollongong, where he worked in a function centre.

Mr Sims, who lived in Wollongong, failed to return home after his shift and did not show up for work the next week.