The 39-year-old posted a Dubsmash video - an app which allows you to lipsync to popular songs and phrases - with her two-year-old son Tennessee to the kid's song Bananaphone.
In true spirit, the famous mum uses a real-life banana as the phone, miming the words to camera before her youngest son makes an appearance.
Before long, Witherspoon is cracking up leaving her son with his own banana to finish the song off.
While Witherspoon sees the funny side of the miming video, her son seems to have serious face on, really trying to concentrate and get the words right. Bless.
She uploaded the video clip to Instagram with the caption: "Good morning! Pick up the banana phone! 🍌#toddlertime #funwithfruit."
The actress is mum to Ava, 16, Deacon, 12, with former husband Ryan Phillippe and Tennessee, nearly three, with husband James Toth.