Fifth Harmony have described their performance with Taylor Swift as a dream come true.

The girl band joined the Blank Space singer on stage in Santa Clara on Friday as part of her successful 1989 world tour. The group sang their hit single Worth It with the 25-year-old and are still pinching themselves over the performance.

'It was amazing! It was honestly - it was a dream come true," Camila Cabello told Entertainment Tonight. 'Sixty-five thousand people in the stadium - and she learned the choreography, wore our tour outfit - it was seriously a night we'll never forget."

Taylor and the girls all donned matching blue costumes for the song. The star loved having the band on stage with her, sharing a photo of them all together earlier in the day.

'Sound check with @fifthharmony right after they taught me their choreo and before they lent me one of their outfits so we could all be twinzies (sic)' she wrote on Instagram.

Taylor has had a number of famous faces join her on stage during her shows, including Cara Delevingne, Lena Dunham and Lorde. The Fifth Harmony girls were not only thrilled to be included but also by how sweet Taylor is despite being such a megastar.

'It was just like a beautiful dream, Just euphoria. So magical!" Ally Brooke said before Lauren Jauregui added, "She was really welcoming. She's really quirky - a cool girl."

The next night Taylor was joined by another girl band, Little Mix, to sing their current hit Black Magic. Fans got an even bigger treat when Pretty Woman actress Julia Roberts and American folk singer Joan Baez joined her on stage during her track Style.