The Latina singer, 51, who was born in New York to Puerto Rican parents, was invited to perform as US President Joe Biden and Vice President Kamala Harris were sworn in at the Capitol, with Lopez performing a medley of This Land is Your Land and America the Beautiful.
Dressed head-to-toe in Chanel, she was accompanied by members of the United States Marine Band.
While performing Woody Guthrie's This Land is Your Land, Lopez delivered a phrase in Spanish, leading those who don't speak the language frantically pulling up Google Translate.
The star in fact quoted from the Pledge of Allegiance, an expression of loyalty to the flag of the US and to America itself.
“One nation, under God, indivisible, with liberty and justice for all," is the English translation of the phrase Lopez chose.
Her bilingual turn was widely celebrated, as fans took to social media to praise the singer, actress and producer for representing the Latinx community at such a momentous occasion.
The star also inserted a lyric from her song Let's Get Loud towards the end of the medley, inviting the assembled crowd to "let's get loud" after she had delivered her message in Spanish.
The day before the inauguration, Lopez met with members of the National Guard who have been protecting the Capitol following the riots of January 6.
Sharing a photo of the meeting on Instagram, she wrote: “What an honour to spend a few moments with these brave men and women. Thank you for your service and sacrifice. I honour you today and everyday. Tomorrow I sing for you and all Americans.”
The Maid in Manhattan actress was accompanied by her partner, former baseball player Alex Rodriguez, with the pair later posing on the steps of the Capitol.
The inauguration is the latest high-profile event Lopez has performed at. Her high-octane halftime show at last year’s Super Bowl alongside Shakira became a fan favourite, and she performed in Times Square for the New Year's Eve celebrations a few weeks ago.
"What's interesting is she's most nervous about Washington, DC," Rodriguez revealed on The Tonight Show Starring Jimmy Fallon this week, "because of the responsibility, and she wants more than anything, like all of us, to bring people together, to inspire."