Andrew Cranswick, the chief executive of African Consolidated Resources, allegedly told US diplomats that Bonyongwe and other officials were looting diamonds from the eastern Chiadzwa diamond fields, according to confidential cables made public by Wikileaks.
This is the first successful Wikileaks prosecution in Zimbabwe.
US diplomatic cables leaked in 2009 named Zimbabwe's central intelligence chief Happyton Bonyongwe as one of several high-profile officials involved in the trade of Chiadzwa diamonds.
Bonyongwe said in court papers that the allegations reached millions of people and were seriously defamatory.
He sued mining boss Andrew Cranswick, who was named in the cables as the source of the allegations.
Cranswick's company, African Consolidated Resources, held the claim to the Chiadzwa diamond fields before they were taken over by panners and then the military.
Rights groups including Global Witness and most recently Partnership Africa Canada claim government officials have been involved in looting the Chiadzwa diamonds, although Bonyongwe has not been mentioned by name in these reports.
Cranswick, who no longer lives in Zimbabwe, says he never spoke to US embassy officials.
But in a judgement Friday High Court Judge Ben Hhlatshwayo ruled Cranswick should pay the 10 million dollars Bonyongwe demanded, plus interest.
In an interview with RFI, Cranswick's lawyer Johnathan Samkange said there's been no attempt to say why Bonyongwe deserves that amount and he will ask for the judgement to be set aside.
But the judgement is likely to encourage other officials linked to President Robert Mugabe's Zanu-PF who have launched lawsuits over Wikileaks.
One of them is Grace Mugabe, the president's wife.