Camila Cabello & Shawn Mendes Slay 'IKWYDLS' on 'Fallon Tonight' - Watch Now!

Camila Cabello looks killer in white while performing with Shawn Mendes on The Tonight Show Starring Jimmy Fallon on Monday night (January 3) in New York City.

The 18-year-old Fifth Harmony beauty and 17-year-old “Stitches” singer performed their hit duet “I Know What You Did Last Summer” with a little help from The Roots.

“@jimmyfallon JEEEEEEMY I LOVE YOU SO MUCH YOURE SO AMAZING. THANK YOU SO MUCH FOR HAVING US. ILL LET YOU KNOW WHEN I STOP FREAKING OUT,” Camila tweeted.

Shawn wrote, “Thank you @jimmyfallon @theroots #IKWYDLSonFallon!!!”

Watch Shawn and Camila‘s amazing performance below!