• Brown has been a divisive figure ever since he pleaded guilty to assaulting then-girlfriend Rihanna in 2009.
• Rowland, accepting the award on his behalf, seemed surprised by the audience's reaction.
Kelly Rowland asked the audience at the American Music Awards to "chill out" after they booed Chris Brown's victory in the best male R&B artist category.
Brown has been a divisive figure ever since he pleaded guilty to assaulting then-girlfriend Rihanna in 2009.
He did not attend Sunday's AMAs after a planned tribute to Michael Jackson was cancelled at the last minute.
Rowland, accepting the award on his behalf, seemed surprised by the audience's reaction.
"Excuse me... chill out," she said as cameras panned to show the audience, some of whom were booing and making other unclear remarks.
Rowland then continued: "But I wanted to tell Chris, thank you so much for making great R&B music and I want to tell him thank you for being an incredible performer.
"I'll take this award [and] bring it to you. I love you. Congratulations. And congratulations to all the nominees in this category."
Brown had been due to honour the 40th anniversary of Michael Jackson's blockbuster Thriller album at Sunday's ceremony in LA, performing hits including Beat It, Billie Jean, Wanna Be Starting Something and Thriller.
No reason for the cancellation was given. Brown himself was taken aback, posting a video of his rehearsal with the caption: "U serious?"
"Would've been the [biggest] AMA performance but they cancelled me for reasons unknown," he added in the comments.
Artists who did perform at the show included Imagine Dragons, Carrie Underwood and Pink - who gave a poignant rendition of Grease's Hopelessly Devoted To You in tribute to Olivia Newton John, who died last month.
Lionel Richie was given the Icon Award, honouring his legacy of hits with the Commodores and as a solo artist.
He was given the prize by fellow Motown artist Smokey Robinson, who joked that he first knew the singer as "the guy with the biggest afro in the Commodores".
Taking the stage, Richie thanked his family and made a point of speaking directly to the "young superstars" in the room.
"God has given you a light. That light is special, that light is only given to a few," he said.
"When you hear the word 'hip,' it means today. When you hear the word 'inspiring,' it means forever. If you get a chance to have that light on you, understand what God has in store."