23 March 2013, 08:33
The '22' star brought the rapper on stage in his hometown for a rendition of the new song.
Taylor Swift was seen performing a duet with Nelly in St.Louis this week.
The 'We Are Never Ever Getting Back Together' singer surprised fans at the Scottrade Center venue when she brought the rapper on stage to join her.
"I'm curious, what would you say if I told you Nelly was here?" she asked the crowd - drawing huge screams.
The pair then proceeded to perform the rapper's new song with the artists sharing vocal duties.
The country star has also been taking to her Twitter account to reveal how much fun she has been having on her latest tour.
She wrote: "St Louis, you were insanely loud and fun and amazing. Thanks for coming, guys. And a huge thank you to @Nelly_Mo for coming out to sing!!!"
Watch Nelly and Taylor Swift performing 'Hey Porsche' together below:
The singer also added: "This tour is making me so happy."
The star kicked off the jaunt earlier this month and released the official music video to her latest single '22' on the same day.
She has been joined by British star Ed Sheeran for the outing – with both stars recently hitting out at rumours they're dating.