Mercedes executive director Toto Wolff has sold five per cent of his Williams shares to Vibra Healthcare's Brad Hollinger.
Wolff left Williams at the end of 2012, swapping to Mercedes where he took up the position of executive director.
But despite leaving Williams, Wolff remained a part owner have bought into the team in 2009.
The Austrian, though, has now sold five per cent to Hollinger, the chairman and chief executive of American-based Vibra Healthcare.
According to Press Association, Hollinger has an option to buy Wolff's remaining 10 per cent stake.
Speaking about the sale, Wolff said: "It was always the plan to reduce the shareholding in Williams towards a level that is clearly a financial investment/
"This was important to Daimler for conflict of interest reasons and for compliance reasons.
"But it was a task to find somebody who was good for the company, who was good for the family, and who had the spirit I had when I joined Williams as a financial investor."