The star-studded party Saturday at the Warwick in Hollywood, Calif., included Kate Hudson, Jennifer Aniston, Justin Theroux, Courteney Cox, Matthew McConaughey, Robert Downey, Jr., Isla Fisher, Conan O'Brien, Chris Martin, Chelsea Handler, Jason Bateman, Nicole Kidman and Tobey Maguire, among others, People magazine reported.
Witherspoon shared on her Instagram account a funny Snapchat video featuring her mother as they made their way to the party, "Crazy on the dance floor? #BirthdayWeekend #MomsInTown," the actress wrote alongside the clip of herself asking her mom if she was going to get crazy on the dance floor.
Hudson shared photos on Instagram from inside the venue posting a photo collage of herself and Witherspoon posing with family and friends. "When you take a [expletive] load of pictures and you still don't have it perfect so you go for the ole collage post....Happy Birthday gorgeous girl @reesewitherspoon !!! Love you," she wrote.
Swift and Keith Urban took the stage to perform for Witherspoon. Swift delivered an acoustic version of "Shake It Off," while Urban was joined onstage by Witherspoon for a rendition of "Sweet Home Alabama," according to Us Weekly.
"Reese didn't leave until 2 a.m.," a source told Us Weekly. "She had the best time and didn't want the night to end."