Matthew Allen was reported missing by his family in November, ABC News reported.
Extensive searches by rescue crews failed to locate him.
Two hikers Saturday discovered Allen lying in dense bushland less than a mile away from Elouera Road.
Allen was extremely disoriented when he was found. He was covered in leeches and bugs and had lost an extreme amount of body weight, police said. He was also believed to suffering from gangrene to his feet and lower legs, police said.
Detective Acting Inspector Glyn Baker said Allen and his family have been reunited.
"His family are ecstatic that he's alive and that he's well," Baker said. "He's been reunited with them and they've been to Hornsby Hospital to see him."
Allen has yet to be questioned on the circumstances that led to his disappearance.