The pop star played the second of five sold-out gigs at the Staples Center, and during her hit Style, she brought out model Sean O'Pry, who starred as her love interest in her Blank Space music video.
Rock and LeBlanc strutted down the long catwalk, waving to fans and dancing as they made their way to the stage in the middle of the arena.
Swift, who has previously professed her love for LeBlanc's hit show Friends, then led the trio as they encouraged the crowd to wave their hands in the air.
Also making surprise appearances at the concert were Mary J. Blige, who sang her songs Doubt and Family Affair with Swift, and Orange Is The New Black star Uzo Aduba, who showed off her singing skills by performing Swift's 2008 track White Horse with the singer.
Aduba previously joined Swift onstage last month (Jul15) during a tour stop in New Jersey, when she strutted her stuff with supermodels during Style.
Swift kicked off her string of 1989 tour dates in Los Angeles on Friday (21Aug15) by inviting Los Angeles Lakers player Kobe Bryant and OneRepublic frontman Ryan Tedder on stage.
She continues the rest of her Staples Center gigs on Monday (24Aug15).