Robert Wood, 52, originally from Glasgow, was found hanging in his upmarket home in Bulawayo in 2012 after a night out at a local pub.
At the time of Mr Wood's death, a Zimbabwean pathologist said the former SAS officer had killed himself. However, Mr Wood's family believe he was murdered.
A coroner in England recorded an open verdict last November, claiming some of the evidence was "very suspicious".
A fresh Zimbabwean inquest, which took place last month, has now ruled out foul play.
Mr Wood's family maintain his girlfriend Henrietta Dube was involved and forged his will, giving her a majority share in his estate.
They claim that following Mr Wood's death, Ms Dube and her Zimbabwean boyfriend took over Goonegough mine and emptied company bank accounts.
However, Magistrate Enias Magate said: "There was no evidence linking Dube or any other person to the death of Robert Wood."
The magistrate added he did not take the disputed will into account "as its authenticity was not subjected to legal determination by a competent court".