The relegation threatened club, which was promoted to English football's top division this season, has been bought by GSE from Adam Pearson, who is to stay on as club chairman.
It is believed GSE's acquisition of Derby County represents a 93% stake, but the team will not incur any extra debt through its acquisition.
GSE will oversee full management of the club, while Tom Glick, a former marketing officer at basketball team the New Jersey Nets and GSE associate, will take on the newly created role of president and chief executive.
It is believed the deal will remove around £25m of the club's debts, while Andy Appleby, chairman of GSE, said the company had vowed to make Derby County "a major force in the Premier League and a global brand recognised around the world."
While Derby County's prospects of staying in the Premier League this season are in severe doubt, GSE will hope the club can make a quick return to English football's top tier if their campaign to avoid relegation this season is unsuccessful.
The GSE acquisition makes Derby County the fourth English Premier League club to become American owned in recent times, after Malcolm Glazer completed his final takeover of Manchester United for around £790m in May 2005.
Aston Villa FC was bought by Randy Lerner for £62.6m in 2006, while Liverpool FC was taken over by Tom Hicks and George Gillett in a consortium bid for £219m in February 2007.