The pair scooped the Video of the Year accolade for their tune 'Hallelujah', and Carrie congratulated John - who wasn't able to attend the ceremony at Bridgestone Arena in Nashville, Tennessee, on Wednesday night (09.06.21) - for winning his "first CMT award".
She said: "Congratulations on what I think is your first CMT award.
"Fans, thank you so much, fans.
"You're the reason that we are all here, doing what we do, doing what we love. Making music videos."
Carrie also tweeted: "Thank you FANS!!! What an incredible night at the @CMT awards! @johnlegend and I took home #VideoOfTheYear !!! Thank you #RandeeStNicholas for your beautiful work...what a night! #CMTawards (sic)"
The ceremony was co-hosted by Kelsea Ballerini and Kane Brown, who took home two prizes on the night - 'Male Video Of The Year' for 'Worship You', and 'Collaborative Video Of The Year' for 'Famous Friends' alongside Chris Young, beating off competition from Carrie and John.
As he picked up the Male Video of the Year gong, Kane said: "This is the most nervous I’ve been all night."
Kelsea also tasted success on the night, winning CMT Performance Of The Year alongside Halsey for their rendition of 'The Other Girl' from the 2020 spectacle.
Upon collecting her first CMT Award, the 27-year-old star said: "After this performance last year, there was a lot of chatter (about) categorically what genre that song did or didn't fit into.
"And the fact that you voted this as the winning performance tells me that you know where my roots are, and that you know who I am.
"It also tells me that you hear music as music. … You love when people push boundaries and explore their artistry. And as I make a new record, that means the absolute world to me."
Taylor Swift - who wasn't able to attend the ceremony - won the fan-voted Best Family Feature accolade for her home footage video for song 'The Best Day (Taylor's Version)'.
CMT announced her as the winner just before the show, and the 31-year-old star tweeted: "I LOVE YOU MOM (sic)"
Carrie, Kelsea, Thomas Rhett, and Miranda Lambert were among the performers at the event.
CMT Music Awards 2021 Complete List of Winners:
Video Of The Year
Carrie Underwood with John Legend - 'Hallelujah'
Female Video Of The Year
Gabby Barrett - 'The Good Ones'
Male Video Of The Year
Kane Brown - 'Worship You'
Duo/Group Video Of The Year
Little Big Town - 'Wine, Beer, Whiskey'
Breakthrough Video Of The Year
Dylan Scott - 'Nobody'
Collaborative Video Of The Year
Chris Young and Kane Brown - 'Famous Friends'
CMT Performance Of The Year
From the 2020 CMT Music Awards - Kelsea Ballerini and Halsey 'The Other Girl'
Best Family Feature
Taylor Swift - 'The Best Day (Taylor's Version)'
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