The 24-year-old has successfully passed a medical at the Madejski Stadium and will be added to a Royals squad which is gunning for promotion to the Barclays Premier League.
And the South Africa international is looking forward to playing for Brian McDermott's side.
"It's amazing to be here," Khumalo said. "It's an unbelievable set-up at Reading - and I just got a great feeling from the club after playing here for Preston at the end of last season.
"I spoke with the manager and he was very ambitious with his plans for the season ahead, so there was only ever one option for me. It just feels right."
McDermott added: "I'd like to thank Harry Redknapp at Tottenham for allowing Bongani the opportunity to come out on loan and for giving us the opportunity to have him here."