Twitter users wondered about the R&B crooner's whereabouts after he was mentioned as a performer in a press release for the charity concert.
On Monday morning, he explained on Instagram that he had to back out of the show because of parental duties.
"So happy to see that last night's concert in Manchester proved that love always prevails," he captioned a photo from the event. "I would have loved to be there but It was my son's first day at Camp Kudzu, one of the few summer camps for kids living with diabetes. This was an important day for him and for myself as a proud father. Stay strong UK."
The artist has been vocal about son Usher Raymond V's battle with type 1 diabetes. "A child that every day has to prick himself and has to be cautious of what he eats and also to carry this disorder around — that really is the type of bravery that we all aspire to have," Usher told People at the Juvenile Diabetes Research Foundation Promise Ball in 2015.
Soon after the attack that claimed the lives of 22 people at Manchester Arena on May 22, Usher took to Twitter to express. "I'm heartbroken by the senseless attack that took place in Manchester," he wrote. "My thoughts and prayers are with those affected."
Prior to addressing his absence, Usher shared an Instagram video Sunday, in which he extended his condolences to the English city. "My heart is with you, Manchester. I'm so sorry for all of your loss and all the pain that you've gone through," he said. "My family and I send our heartfelt condolences to each and every one of you in this difficult time. We need to love each other. We need to be good to each other. Stay strong and united because only through that love can we help each other heal."
Headliner Grande was joined by Miley Cyrus, Justin Bieber, Katy Perry The Black Eyed Peas, Niall Horan, Pharrell Williams and more.