The 39-year-old was found by dogs with a search and rescue team about 7 o'clock last night.
Mr Fong, who had been missing in the bush since last Saturday afternoon, was found in the southern part of the ranges, near the Mangatangi dam.
Search and Rescue co-ordinator Sergeant Dene Duthie said he was tired, hungry and cold when they found him.
"He was still walking ... and talking. It seemed he had just kept going through sheer determination.
"His feet were in pretty bad shape as they had been wet for most of the time ... but he had a little more food than we initially thought so that kept him going."
Mr Duthie told the Herald one of three search and rescue dogs picked up Mr Fong's scent during yesterday's daylight searches, so the search was kept going after dark.
"There were about 20 people in the bush after dark ... but there would have been 50 to 60 people out searching during the day.
"He was so grateful when we got to him."
Mr Duthie said Mr Fong, a bio-engineer at Middlemore Hospital, was wearing shorts and a light, water-proof jacket.
"He did really well to keep going and it had just started raining when we found him as well."
The search and rescue co-ordinator said Mr Fong told rescuers he tried to remain active throughout his three-night ordeal, as he was afraid of getting too cold.
"He tried to take shelter on the first night but said it just got too cold, so he decided to just keep moving."
Mr Duthie said Mr Fong was driven to Waharau base, in the eastern area of the Hunuas, and reunited with his family.
"They were obviously very happy to see him."
After being assessed by medical staff, Mr Fong was given the all-clear to be taken home.
"He was wrapped in blankets when I saw him and seemed okay."
Mr Duthie said Mr Fong would be seen by a doctor today.
Mr Fong, an experienced tramper, set out for a four-hour walk from Hunua Falls on Saturday morning, and was to be picked up at 3pm.
At 3.30pm he texted his younger brother, saying: "Gonna be late so don't call SAR [Search and Rescue]."
Following his instructions, family members waited until after 9pm to return to the arranged meeting point.
But they found no sign of him and two hours later, when he didn't answer his phone, they alerted authorities.
Speaking yesterday before Mr Fong was found, his sister, Margaret Kumar, said the ordeal had taken its toll on the family.
"My brothers are slowly breaking down and for myself, I'm starting to crack today. I'm really freaking out."
Mr Fong carried a backpack with a bottle of water, Powerade and a box of Nutri-Grain into the bush.
He was in a good mood and looking forward to the tramp, Ms Kumar said.
He usually went with friends but as no one was free to go with him that day, he decided to go alone.
She said her brother, who tramped weekly, would have been resourceful in the bush.
"He'll probably panic for a little while, then I know he'll figure out, 'I've got to stay alive'."
- Teuila Fuatai, NZ Herald
