She beat out Dierks Bentley, Eric Church, Brandy Clark and Lee Ann Womack for the awards.
"I love every album in this category," an emotional Lambert said from the stage as her husband, Blake Shelton, beamed from the audience. "I am so thankful for this. I poured my heart and soul into this record ... Thank you so much for this amazing night. I love y'all."
Lambert was a multiple nominee this year; she was also up for Best Country Song, Solo Performance and Duo/Group Performance.