Greenwood performed his signature song God Bless America for an incoming Republican administration for the fourth time, when he took the stage at the Make America Great Again! Welcome Celebration at the Lincoln Memorial in Washington, D.C. as Trump and his family looked on.
Keith was also a big highlight at the country music-heavy event, singing a medley of his hits including An American Soldier, Made in America, and Courtesy of the Red, White and Blue (The Angry American).
He also saluted the military and thanked outgoing President Barack Obama, before welcoming the President-elect.
Soul legend Sam Moore kept the patriotic theme going with his rendition of America the Beautiful.
The pre-inaugural event kicked off with actor Jon Voight offering up a welcome speech.
The Oscar winner said, "We have all been witness to a very gruelling year and a half for the President-elect. We have been witness to a barrage of propaganda that left us all breathless with anticipation, not knowing if God could reverse all the negative lies against Mr. Trump, whose only desire is to make America great again."
He added, "God answered all our prayers. Because here it is. We will be part of history, all of us."
Meanwhile, stars like Robert De Niro and Michael Moore headlined an anti-Trump demonstration outside the Trump Hotel in New York City as the Make America Great Again Welcome Celebration was going down in the capital.
Trump will officially be sworn in as the 45th President of the U.S. on Friday (20Jan17).