The verdict led to an urgent review by the UK's Crown Prosecution Service (CPS) as charges against nine journalists accused of making illegal payments to public officials were also dropped.
The CPS confirmed it was scrapping the cases of nine out of 12 journalists awaiting trial.
Those who will no longer face prosecution under Operation Elveden include former 'News of the World' editor Andy Coulson.
The journalists found not guilty in court included former Daily Mirror reporter Graham Brough and the Sun tabloid's Neil Millard, Brandon Malinsky and Tom Wells were cleared of "conspiring to commit misconduct in public office".
Millard, 33, Malinsky, 50, Brough, 54, and Wells, 34, had all denied charges of paying public officials for stories.
The trial is part of Scotland Yard's 'Operation Elveden' into allegations of inappropriate payments to police and public officials.
It followed revelations around illegal phone-hacking at media tycoon Rupert Murdoch's 'News of the World' tabloid, which has been shut down since.
Speaking outside court, Millard said his heart had been "pounding and pounding" while standing in the dock as the verdicts were read out.
The four journalists are the latest reporters to have been tried on charges brought under Operation Elveden.
All of them had denied various counts of conspiring to commit misconduct in a public office and bribing public officers in return for information for their newspaper reports.
Last month, four 'Sun' journalists were cleared of wrongdoing over paying public officials for stories.
The controversial police investigation into newspapers' dealings with public officials is believed to have cost an estimated 20 million pounds.
Thirteen journalists have been acquitted.
