Pete Cresswell was forced to leave Liverpool University without graduating for protesting against its investments in apartheid-era South Africa.
The student was one of 10, including Channel 4 News presenter Jon Snow, punished for a six-week sit-in at the university's Senate House.
Mr Cresswell said he was "gobsmacked".
"If I went back through it 1,000 times, my 22-year-old self in 1970 would do it again," said Mr Cresswell, who was the only one of the 10 to be expelled.
The former politics student said he was "astonished" to be awarded a degree and had always thought "hell would freeze over" before the university gave him one.
Awarding him an honorary Bachelor of Arts degree at Liverpool Philharmonic Hall, vice chancellor Prof Janet Beer said "we in the university want to put this right".
She said that while the university "cannot undo" Mr Cresswell's "unfair and wrong" treatment, it can "recognise that wrong, and publicly do so" to a man who "saw what was the right thing to do and paid a price for it".
Inspired by the 1968 student revolts in France, activists across the UK brought protests and sit-ins to universities into the early 1970s and students in Liverpool were no exception.
The chancellor of the university at the time was Lord Salisbury, a known supporter of apartheid.
Mr Cresswell said: "Looking back, I think we were right and if you look at the issues, we have been proved right.
"This does put a full stop on the whole thing and I just feel pleased that a bit of history has been reviewed and put to bed."
The Birmingham-born student stayed in Liverpool and despite having to leave his politics course during his third year with a "CV from hell", eventually became a social worker, holding roles with the council and the Care Quality Commission.
Now retired, Mr Cresswell said he was pleased his daughter had had the chance to see him in robes - she graduated herself more than 10 years before him.
Mr Snow, who received an honorary degree from the university in 2011, sent him a congratulatory video message, saying: "Well done Pete. Well done Liverpool - I still love you."
Mr Cresswell said that while Mr Snow could not attend, he was "there in spirit".

The cases were re-opened after officers heard tapes seized from the American university, the BBC understands.
The murders being re-examined are those of John Benedict Devine in July 1989 and John Joseph O'Hara in April 1991.
No-one has ever been charged in connection with the two murders.
It is the first time loyalist killings have been investigated as a result of details in the Boston tapes.
Police say the two men were killed simply because of their religion.
Mr Devine, a 37-year-old father-of-three, was shot in front of his 13-year-old son at his home in Fallswater Street in west Belfast.
Mr O'Hara, a father-of-five, was working as a taxi driver when he was shot in Dunluce Avenue in south Belfast in April 1991.
Police have said they have new information that could help them to catch the killers.
"As a result of information we have recently received, we believe we are now in a position to progress both of these investigations.
"However, we need the help of the public," said Det Insp Neil McGuinness.
The Police Service of Northern Ireland will not comment on the nature of the new information.
But the BBC believes the decision to re-open these cases was taken after detectives listened to tapes seized from Boston College in recent months.
Dozens of former paramilitaries, most of them republican, gave interviews to university researchers compiling an oral history of the Troubles.
They did so on the understanding that the tapes would not be made public until after their deaths.
But police took legal action and were granted permission to access some of the recordings.
It is understood police believe information contained on some of the seized tapes could help them identify those responsible for these two killings.
Detectives are now trying to find other supporting evidence.
They have appealed to anyone with information about the killings to come forward.
A student who was expelled from university for taking part in anti-apartheid demonstrations in 1970 has been awarded an honorary degree.
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Police are re-investigating the murders of two Catholics because of information from interviews about the Troubles by former loyalist paramilitaries for a history project by Boston College.