The two recently wrapped their upcoming HBO series Big Little Lies and it sounds like things went really well.
"I love her," Kidman told E! News at the New York premiere of her new drama Genius (in theaters on June 10). "We had such a great time."
And that included their wrap party. "It was beautiful," Kidman said, adding that they spent some time "crying and hugging" during the bash.
Witherspoon also captured some of their dancing on Snapchat.
Now that Kidman has lived in Witherspoon's native Tennessee for quite some time, does she consider the Aussie a "southern girl" now?
"I hope so," Kidman said with a smile. "We have so much in common and we're very close. I'm lucky to have her as such a good friend."
The seven-episode Big Little Lies, directed by Witherspoon's Wild director Jean-Marc Vallée, is based on the bestselling novel of the same name. Co-stars include Laura Dern, Shailene Woodley and Zoë Kravitz.