The Panorama episode was previously postponed due to legal action brought by Mr Mahmood.
He had argued in court that revealing his current appearance would breach his human rights by exacerbating the existing risk to his safety caused by his investigative work.
But the High Court did not grant Mr Mahmood an injunction to stop the screening and that decision was upheld by the Court of Appeal on Monday.
The BBC One programme contained video of Mr Mahmood in a car and presenter John Sweeney said it was “footage of him on a sting”.
He added: “Our investigation has revealed serious wrongdoing at the heart of some of his undercover stings.
“We’re identifying him tonight to make it more difficult for him to entrap people in the future.”
The programme, described by Mr Mahmood’s counsel Justin Rushbrooke QC as a “hatchet job”, claimed to shed light on the methods used by the reporter. He exposed various personalities while working at the now defunct News Of The World, using his disguise as a sheikh.
He was criticised after the collapse of the drugs trial of pop star Tulisa Contostavlos in July, when a judge said there were grounds to believe he had lied.
Former Attorney General Lord Goldsmith told Panorama that Mr Mahmood’s record of convictions needs to be re-examined.
“The fact that somebody who has been accused by a judge of apparently not telling the truth may be instrumental in those convictions would certainly be a reason to look at those convictions again and to examine them to see whether they are safe,” he said.
The programme claimed that Mr Mahmood’s name cropped up when a 1999 covert police operation - part of a murder inquiry - revealed links between corrupt police officers, a firm of private detectives called Southern Investigations and tabloid journalists.
A document seen by Panorama said: “Source met Maz, a News of the World reporter... on this occasion Maz was with a plain clothes officer... the officer was selling a story to Maz.”
Panorama questioned why a full scale inquiry did not take place into police officers selling stories to tabloid journalists.
Mr Mahmood denies buying stories from police officers.
A Scotland Yard spokesman said: “The MPS (Metropolitan Police Service) does not commission work from investigative reporters nor instigate their work.
“However, regardless of source, once we have been presented with evidence that a crime has been committed we have to assess it to decide whether the circumstances warrant police investigation.”
He added: “We are currently investigating Mazher Mahmood on suspicion of perverting the course of justice, after the trial of Tulisa Contostavlos was halted at Southwark Crown Court in July 2014.
“It would be inappropriate to comment any further until that investigation is complete.”
The programme also featured the case of Page Three girl Emma Morgan.
She was targeted by Mr Mahmood in the 1990s and thought she was being offered a lucrative contract for a Middle East bikini calendar.
But, according to Panorama, the reporter wanted a story exposing her as a drug pusher and hired a man called Billy to assist.
Ms Morgan, who was 24 at the time, told the programme she was put under pressure for several hours to pick up cocaine from Billy and give it to Mr Mahmood.
“I was a fool, I was naive. To be foolish isn’t a crime, to be naive isn’t a crime. To do what he did is criminal,” she said.
“I haven’t had the career I should have had, I haven’t had the life I should have had. He’s a horrible, horrible man.”
Billy said: “I’d like to apologise to Emma for my part in stitching her up. The only real criminal was Mazher Mahmood. He gave me the money to buy the cocaine.”
Solicitor Mark Lewis, who helped expose phone hacking at News International and is now representing some of the people investigated by Mr Mahmood, told Panorama: “The damage that’s caused, the damage for people’s livelihoods, the amount of people have been sent to prison, is much, much bigger. It’s a far more serious thing than phone hacking ever was.”
Mr Mahmood, who denies any wrongdoing and has not been charged, issued a statement yesterday asking people to “keep an open mind on any allegations”.