Kile Glover, the 11-year-old son of the singer's ex-wife Tameka Foster, died last month after a jet ski accident in Georgia, reported Contactmusic.
Usher made his first public performance following the tragedy at a star-studded charity event in New York over the weekend to raise millions of dollars for the Big Apple's famed Apollo Theater.
"For all the hard times, you can't do it without your friends, so I just want to toast a second... Thank you for allowing me to share this incredible moment with you... Cheers for tears," he said. Sir Paul McCartney also made an appearance at the event, and Jennifer Hudson performed a medley of Whitney Houston's hits.
The gig raised more than USD 2 million for the famed theatre, which is credited with helping launch the careers of stars including Ella Fitzgerald, Billie Holiday and James Brown.