Three women had accused Mr Ghomeshi of attacking and sexually assaulting them.
Mr Ghomeshi, 48, had denied the charges, describing the encounters as consensual "rough sex".
The judge said that the three complainants' stories had been inconsistent and said reasonable doubt existed in this case.
A group of protesters - holding slogans "We believe survivors" - later gathered outside the court building in Toronto.
Ghomeshi trial rattles assault survivors
The alleged assaults took place between 2002 and 2003.
"Each complainant was less than full, frank and forthcoming in the information they provided to the media, to the police, to Crown counsel and to this Court," Justice William Horkins wrote in his judgement.
"The evidence of each complainant suffered not just from inconsistencies and questionable behaviour, but was tainted by outright deception," he said.
"At the end of this trial, a reasonable doubt exists because it is impossible to determine, with any acceptable degree of certainty or comfort, what is true and what is false."
The trial, which attracted a flurry of media attention, has spurred debate about how victims of sexual assault are treated by the Canadian legal system.
A demonstration in support of victims of sexual assault happened after the verdict was read, according to reports on Twitter.
Mr Ghomeshi's three accusers came under intense scrutiny from the defence during the eight-day trial, with defence lawyer Marie Henein questioning why they remained in contact with or on good terms with Mr Ghomeshi after the alleged assaults.
One sent Mr Ghomeshi a picture of herself in a bikini after she said he had punched her in the head. She told Ms Henein that she had wanted to bait Mr Ghomeshi into incriminating himself.
But prosecutor Michael Callaghan said "post-assault contact was not relevant to the sexual assault that took place" and every victim coped with assault differently.
Some advocates for sexual assault victims worried that the women were being put on trial rather than the alleged attacker.
Others were concerned the scrutiny would discourage other victims from coming forward in future cases.
Mr Ghomeshi, who hosted the radio show Q, was sacked by Canadian Broadcasting Corporation (CBC) in 2014 after the allegations became public.
The CBC began an inquiry into Mr Ghomeshi's sexual activities after the Toronto Star newspaper began investigating allegations by an ex-girlfriend that he had engaged in non-consensual, violent sex with her.
The report found that CBC management knew about Mr Ghomeshi's behaviour, or should have known. It said the members of management did not take steps to stop it.
A number of women came forward after the Star's report, accusing him of punching, strangling and battering.
Jian Ghomeshi, who was once one of Canada's top broadcasters, has been found not guilty of sexual assault and choking his victims.