Director of Criminal Investigations George Kinoti on Wednesday evening said the suspect; Rebecca Mueni Musau was arrested while attempting to flee to Tanzania.
Kinoti said after interrogation, Mueni took the detectives to her home in Nairobi where police recovered Ksh.13 million.
Two other suspects wanted in Dubai over the Ksh.140 million heist are said to have escaped the police dragnet.
The DCI boss said the three were part of six guards of a private security company who were escorting the cash on transit in May this year.
Kinoti said after the heist, the International Criminal Police Organization (Interpol) contacted Kenya to help in arresting the suspects.
He added that the suspect had confessed to have used part of the loot to purchase property and build palatial homes in Nairobi.
Kinoti said the suspect will be extradited to Dubai for prosecution.