The British star and actress limbered up for the "toddlerography" session on The Late Late Show and it soon became evident that James couldn't keep up.
"I know you think you're in shape but these instructors are going to beat you down," James warned Kate at the start of the class.
"I think I'll be fine," replied Kate, as she stretched and warmed up in her colourful leggings and white cut-off top.
"These instructors are a nightmare," James continued. "They made Dwayne Johnson cry, The Rock. They made The Rock cry."
"Well, who are the instructors?" asked Kate.
The camera then panned to an adorable little girl, who waved hysterically at the two stars.
Kate proved a natural, leaping, twirling and shimmying around the room as she and a group of children danced to Natalie Imbruglia's Torn. James, meanwhile, struggled slightly and couldn't manage a somersault.
After all the hard work, the session naturally ended with a cool down and a nap.
Kate is the latest celebrity to star in the hilarious The Late Late Show segment. She posted a snap on Instagram with James, writing: "Got to dance with my friend @j_corden on @latelateshow tonight!! Always a blast."
Gwyneth Paltrow, Jenna Dewan Tatum and Jason Derulo are among the other celebrities who have featured in the segment.