A power surge at the plant led to explosions, and a meltdown, which spewed massive amounts of radiation into the atmosphere.
The immediate aftermath saw 31 people die and more than 300,000 more displaced.
Alexander Vainer was working as a builder on renovations for a children's holiday camp just 30 kilometres from the reactor.
Now nearly 80, he lives in Melbourne.
When the accident happened, his supervisor told the workers they couldn't leave.
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"Instead of renovating the children's camp, we had to turn it into a field hospital," he told SBS News.
They were there for two weeks.
"We had cars driving from the Chernobyl area into our place every day," Mr Vainer said.
"They were in Chernobyl for a whole day and then would come and leave the cars in the camp for a night and the drivers would change.
"We actually all have certificates that state that we are the victims of Chernobyl."
"No one would work twice [driving into Chernobyl].
"They looked just fine, but what happened to them after, God only knows."
Musician Roman Korchev was another survivor who moved half a world away to Melbourne
A resident of Kiev, he was a 16-year-old, fishing with his brother on a lake 150 kilometres from Chernobyl when military helicopters started flying overhead.
"Lots of people thought it was a third world war," Mr Korchev said.
He fled with his family and thousands of others to southern Ukraine.
When he arrived, he was ordered to visit a doctor. His head was shaved and he was given "a special bath".
"I have no idea what it was," he said.
Mr Korchev attributed a major heart problem to the accident.
He's had two operations on his heart, and said the doctors could not explain why he was so unwell.
"My heart valve was calcified, which doesn't often happen, it's a mystery," he said.
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After the accident, radiation spread from the plant, over the western Soviet Union and into Europe.
Many of those in its path received "Chernobyl payments", government compensation for any future health problems arising from the accident.
Anastasia Tarasova, 30, still receives $10 a month "compensation" from the Russian government.
"We actually all have certificates that state that we are the victims of Chernobyl," she said.
"But the amount of radiation has been left blank.
"Most of us have thyroid gland problems."
But some have argued that Chernobyl's impact has been massively overstated.
UNSW Nuclear engineering lecturer, Dr Patrick Burr said there had been 10,000 cases of thyroid cancer recorded since the Chernobyl disaster.
He said that number was projected to rise to 16,000, but most of those people were expected to survive.
"We expect the death toll from thyroid cancer to be as high as only 160 people," Dr Burr said.
However Mr Vainer still believes the accident ruined his health.
"I was a phenomenally healthy man," he said.
"Now I'm almost nothing."
"It's a blessing that I'm still alive."
Today, reactor number four is entombed in cement and the nearby city of Pripyat is a macabre tourist attraction.
Those left behind hope Chernobyl's legacy will never be forgotten.
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