According to the marathon star, his real name is Hussein Abdi Kahin and he was given the name Mohamed Farah by those who flew him over from Djibouti.
He was flown over from the African country aged nine by a woman he had never met, and then made to cater for another family’s children, he says.
“For years I just kept blocking it out,” the Team GB athlete says.
“But you can only block it out for so long.”
Previously he said he came to the UK from Somalia with his parents as a refugee.
But in a documentary by the BBC and Red Bull Studios airing on Wednesday, July 13, he said his parents have never been to the UK while his mother and two brothers live on their family farm in the breakaway state of Somaliland.
He said his father, Abdi, was killed by stray gunfire when Mo was four years old, in civil violence in Somalia.
He says he was about eight or nine years old when he was taken from home to stay with family in Djibouti. He was then flown over to the UK by a woman he had never met and wasn’t related to.
She told him he was being taken to Europe to live with relatives there – something he says he was “excited” about. “I’d never been on a plane before,” he says.
He says she had fake travel documents with her that showed his photo next to the name “Mohamed Farah”.
When they arrived in the UK, the woman took him to her flat in Hounslow, west London, and took a piece of paper off him that had his relatives’ contact details on, according to the documentary.
“Right in front of me, she ripped it up and put it in the bin. At that moment, I knew I was in trouble,” he says.
“if I wanted food in my mouth”. He says the woman told him: “If you ever want to see your family again, don’t say anything.”
“Often I would just lock myself in the bathroom and cry,” he says.
For the first few years the family didn’t allow him to go to school, but when he was about 12 he enrolled in Year 7 at Feltham Community College.
School staff were told Sir Mo was a refugee from Somalia.
His former teacher Sarah Rennie says he came to school “unkempt and uncared for”, that he spoke very little English and was an “emotionally and culturally alienated” child.
She says the people who said they were his parents didn’t attend any parents’ evenings.
Sir Mo says sport was a lifeline for him as “the only thing I could do to get away from this [living situation] was to get out and run”.
He told his PE teacher Mr Watkinson about his true identity, his background, and the family he was being forced to work for, who contacted social services and helped Sir Mo to be fostered by another Somali family.
“I still missed my real family, but from that moment everything got better,” Sir Mo says.
“I felt like a lot of stuff was lifted off my shoulders, and I felt like me. That’s when Mo came out – the real Mo.”
Mo made a name himself as an athlete, at the young age of 14 he was invited to compete for English schools at a race in Latvia – but he didn’t have any travel documents.
His PE teacher Watkinson helped him apply for British citizenship under the name Mohamed Farah, which was granted in July 2000.
In the documentary, barrister Alan Briddock tells Sir Mo his nationality was technically “obtained by fraud or misrepresentations”.
“I had no idea there was so many people who are going through exactly the same thing that I did. It just shows how lucky I was,” he says.
“What really saved me, what made me different, was that I could run.”