Kāpiti man Duncan Hill was last seen at his home in the Ōtaki Gorge area on 5 October by his landlord.
Senior Sergeant Sam Gilpin said the 59-year-old has not been seen or heard from since and left his vehicle and personal items at home.
"He has limited mobility due to a back injury, and his loved ones are understandably concerned.
"Police Land Search and Rescue, along with family, have completed searches of the immediate surrounding area, however it is difficult terrain and an isolated area."
Police are now seeking the public's help with information on his location.
Hill is described as Caucasian, 185cm tall, and of a stocky build with short greying hair.
"Duncan has been known to spend periods of time alone or in the company of spiritual groups.
"Police and his family would like to know that he is safe and well."
Police want anyone who has seen Hill to call 111 immediately, quoting the file number 231008/9780.