The 73-year-old Apprentice star explained that his sibling had been killed by the Covid-19 virus.
The business magnate shared his sad news with fans and followers.
Lord Sugar tweeted: “Today I lost my long suffering brother Derek another victim of Covid which added to his underlying health issues. He was a life time passionate Spurs supporter.”
He added, “It’s a sad day for us all in the family.”
Lord Sugar’s update was immediately met with messages of support from followers.
One tweeted back: “May his memory be a blessing. Sincere condolences.”
Lord Sugar was chairman and part-owner of Tottenham Hotspur football club from 1991 to 2001.
He sold his remaining stake in the club in 2007 for a reported £25 million.