Cascade Investment, a firm owned by Bill Gates that manages assets exclusively for the Bill & Melinda Gates Foundation Trust, had last June disclosed a stake in G4S, when its holding crossed the 3 percent threshold for the first time.
A filing on May 28 showed the holding was reduced below 3 percent, and a spokesman for the Gates Foundation told Reuters on Saturday it no longer held any interest in G4S.
G4S declined comment.
G4S, which runs services such as cash transportation and prison management in more than 125 countries, is in the middle of overhauling its sprawling business, shaking up management, cutting costs, improving customer service and restructuring weak divisions to help revive its fortunes.
Having failed to provide enough security guards for the London 2012 Olympics, G4S suffered another scandal last July when, alongside rival Serco Group Plc, it was banned from new UK government work after being found to have charged for monitoring criminals who were dead, in prison or not tagged at all.
On Thursday G4S's own security guards ejected protesters from its annual shareholders' meeting, after they criticised the company's work in Israel, where it provides security at prisons and occupied Palestinian territories.
Gates's investments range from stakes in the Canadian National Railway Co to drinks group Diageo Plc.
The Bill and Melinda Gates Foundation works to eradicate the world's most deadly diseases and poverty.