The four men had been found guilty of misleading the stock market during the 1987 takeover by Blue Arrow of the Manpower group.
The judges, headed by Lord Justice Mann, said that explanations for their decision would be given later.
The four advisers were given suspended jail terms last February for plotting to deceive financial markets during a rights issue designed to raise money from Blue Arrow shareholders to finance the British recruitment agency's bid for the much larger rival agency in the US.
Jonathan Cohen, Nicolas Wells and David Reed had been given 18-month sentences suspended for two years after being found guilty of conspiracy to defraud. A fourth defendant, Martin Gibbs, was sentenced to 12 months' imprisonment, also suspended for two years.
A jury had found that they rigged the stock market in 1987 while trying to disguise the failure of the record pounds 837m rights issue.
The Court of Appeal heard argument during a two-day appeal that the trial had been unfair because of the weight and complexity of the case presented to the jury, and because the trial judge, Mr Justice McKinnon, limited his summing- up to one issue and told the jurors to ignore 75 per cent of the evidence. The Crown argued that Mr Justice McKinnon kept 'constant vigilance' on the manageability of the case.
The judge's decision to limit the summing-up worked to the advantage of the defendants, and there was no evidence that the length and detail of the case caused the jury any difficulty, the Crown argued.
After the Court of Appeal's ruling, Mr Reed said: 'I am absolutely delighted. It has been three long years.'
Asked if he had thought he would win the day, Mr Reed said: 'You don't think at this stage. I've had my hopes built up before.' Mr Cohen said: 'For the moment I am delighted. I can't make a further statement until I've seen the judgment, but I shall want to say something then because I feel strongly about a lot of matters in this case.'
Mr Gibbs said: 'I am delighted of course, but this is much more important for the others than for me.
'They are younger men who have families and still have careers. I retired three years ago but I am glad to have my name cleared.'
The court's decision to quash the Blue Arrow convictions casts further doubt on the future of complex fraud trials. The Government promised an urgent review of serious fraud cases after the collapse of the second Guinness trial in February.
However, reform now appears unlikely until after the Law Commission and the Royal Commission on criminal justice have reported next year.
At the end of the year-long Blue Arrow trial, which cost more than pounds 30 million, Mr Justice McKinnon called for reform to prevent such lengthy hearings in future.Reuse content