Luke Shambrook, 11, was taken to hospital Tuesday after being treated on the scene for dehydration and hypothermia. Despite a few small scratches, he was uninjured.
"To spot him now is an absolute relief and the joy by all of us that he's been found is just hard to describe," Victoria Police Acting Commander Rick Nugent told reporters, according to CNN affiliate Seven, adding that cold and wet weather made it all the more unlikely that search and rescue teams would find the boy alive.
"In some ways it's a miracle," he added.
Ground and air teams, including volunteers and canine units, scoured the area for four days. The boy was spotted by police helicopter around three kilometers (1.9 miles) from the campsite where he was last seen on Good Friday.
"Out of the corner of my eye I caught a flash of something," Acting Sergeant Brad Pascoe from Police Air Wing said of the moment he spotted Shambrook in a video released by Victoria Police on the organization's Facebook page
"When we had turned around and got a better look at him we saw that it was a person on the ground. We were obviously over the moon, all of us in the crew are parents ourselves and we can only imagine what the parents of Luke have been going through and it's just such a great reward for everybody's efforts."
Clue found Monday
Police found a hat belonging to Shambrook on Monday, raising hopes that he might be found safe.
His family had warned police and search crews that, due to his condition, he may not have even been aware that he was considered missing.
Rescuers were ecstatic that he had been found relatively unscathed.
"An 11-year-old boy, challenged as he is with his autism, he's a courageous, resilient, strong young man," Nugent said.
"Everyone is overwhelmed by the news... the longer it went the more challenging it was going to be for us. To find him safe and well... is just wonderful news."