The outspoken and acerbic British journalist and TV personality had criticized her for leaving the U.K. immediately after a suicide bomber killed 22 people and injured dozens more at her Manchester Arena show, instead of staying and visiting the wounded survivors.
Grande had returned to the U.S. to be with her family and flew back to England last week, where she did visit injured fans at the hospital ahead of the One Lone Manchester concert, which she co-organized.
"I misjudged you, @ArianaGrande & I apologize," he wrote on Twitter, alongside a screenshot of Grande embracing a child singer onstage after performing with her choir. "You're an admirable young woman & this is a magnificent night. Respect. #OneLoveManchester."
Many people praised Morgan for apologizing and some expressed shock over it.
Piers Morgan, admitting he was wrong... well I'll be damned— Cerys? (@CerysPoole) June 4, 2017
had to blink twice to make sure— Adrian (@Adr_ian07) June 4, 2017
"I thought Ariana Grande was wrong to fly off after #ManchesterAttack," Morgan tweeted. "But tonight she's putting on a fabulous show. #OneLoveManchester."
Grande was joined onstage at the One Manchester Concert by the likes of Miley Cyrus, Coldplay, Justin Bieber, Katy Perry and the Black Eyed Peas, with whom she sang their breakout hit "Where Is the Love?"