Underwood's performance was slightly delayed by equipment malfunctions, though that didn't stop the country star as she broke out into "America the Beautiful" a cappella.
The crowd, including former President Joe Biden could be seen mouthing along to the words as she sang.
The audience erupted with applause after her performance. After she finished, Underwood turned around to greet Joe Biden, flanked by Harris, who appeared to be praising her performance. Underwood shook the former president's hand before skipping Harris and moving directly across the aisle to shake President Trump's hand instead.
Underwood was announced to perform at the inauguration last week, and was subsequently inundated by leftists who dragged her for being friendly with Trump.
"Heartbroken. Always loved you. Won't support your actions," wrote another angry fan.
Brett Cooper, formerly of The Daily Wire, noted that Hillary Duff had previously performed at President George W. Bush's second inauguration in 2005.
"Did she get canceled? Did she get called a bigot and a traitor because she performed for a Republican president?" Cooper asked. "No. People loved her, Bush said she was awesome, it was fun."
"Let’s bring that energy back. It’s an insane opportunity, a historic moment, and Carrie Underwood will crush it," she added.
The country star explained her decision to performa at the inauguration in a statement, emphasizing unity.
“I love our country and am honored to have been asked to sing at the Inauguration” she said.
"I am humbled to answer the call at a time when we must all come together in the spirit of unity and looking to the future," Underwood added.
