Underwood also won the honor last year.
Brad Paisley took home the prize for Top Male Vocalist and Miranda Lambert the trophy for Top Female Vocalist.
This is Paisley's fourth consecutive win in the category and Lambert's first.
Lambert also won the Album of the Year honor for her CD "Revolution" and the Video of the Year gong for her song "White Liar."
Brooks & Dunn earned the Top Vocal Duo title and, in addition, they sang the fan-selected song "My Maria" as their final Academy of Country Music Awards performance. The musicians recently announced plans to disband.
Lady Antebellum picked up the prize for Top Vocal Group, as well as the awards for Single Record of the Year and Song of the Year for "Need You Now."