Jason Houston, 32, was reported missing by a friend after he left his residence and failed to return on Sunday, October 2.
Police said Mr Houston is believed to have travelled to Kotara on the day he went missing.
He has ties to the Central Coast, Newcastle, Lake Macquarie and Murwillumbah.
Mr Houston is described as caucasian, with a slim build, about 175cm tall, with light brown hair, a goatee beard and bad teeth.
He was last seen wearing a short-sleeved shirt, jeans and white sneakers.
Police conducted patient records at multiple hospitals but were unable to locate Mr Houston.
Police are appealing to the public for any information surrounding his disappearance.
Anyone with information that can assist is urged to contact Lake Macquarie Police or Crime Stoppers on 1800 333000.