Police hope the Israeli man missing in the Buckland Peaks area, near Westport has military training.
A search and rescue operation is under way after the 49-year-old went missing on Tuesday.
He's believed to have entered the Paparoa National Park at 10am, wearing dark trousers and a red jacket.
Senior Constable Mike Tinnelly says police have concerns for his safety.
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He says the weather's cold, but they're hoping, as with many Israeli citizens, he's got some military training behind him.
Police ask that anyone who has been in the Paparoa National Park area in the past few days who may have seen a man matching this description to get in touch with them immediately on 03 789 7905.