Bernard Thomas, 63, was pulled from the rubble when coal slurry slid on to the Pantglas primary school in Wales on 21 October 1966.
In total 144 people died in the tragedy, including 116 primary school children.
His brother Andrew told the BBC he had “faded away” in hospital on Wednesday, ten minutes after removing his oxygen mask to eat breakfast.
He said: "Bernard was a real character and his death has come as a shock to us as a family and the community of Aberfan."
"We can't be sure where he caught Covid, but he had an eye appointment at the Royal Glamorgan hospital on 21 December.
"A few days later, he became ill and at Prince Charles hospital, he tested positive for Covid-19."
Andrew said they had spoken regularly on the phone and he told him he was getting better.
Bernard was diagnosed with post-traumatic stress 50 years after the Aberfan disaster and told S4C he "still heard the sounds of children screaming."
He lived with his 90-year-old mother Gwen before he died and had a second brother called Robert.
Meanwhile, the coronavirus death toll in the UK has passed 80,000, with a further 1,035 people being confirmed dead on Saturday within 28 days of testing positive.
There were also another 59,937 daily cases, bringing the total number of infections to 3,017,409, according to official data.
Doctors have warned pressure on the NHS could get worse in the coming weeks, as figures for cases, hospital admissions and deaths hit record highs.
The government has doubled down on its “stay at home” message by launching a new advert, fronted by England’s chief medical officer Professor Chris Whitty, urging everyone in England to “act like you’ve got” coronavirus.
Cases were estimated to have been as high as 100,000 per day at the peak of the first wave in April.
But scientists advising the Government estimate there are currently more than 100,000 new infections per day and possibly higher than 150,000 which they believe puts the current number of daily cases at a higher level than ever during the pandemic.
They believe the current lockdown may lead to a plateau of cases of coronavirus across the UK rather than the dramatic cut seen following the March and April lockdown.
Government death figures continue to be affected by a lag in the publication of recent data and will contain some deaths that took place over the Christmas and New Year period that have only just been reported.
Watch: What is long COVID?