She wrote songs for Aussie singer Natalie Imbruglia's third studio album Counting Down the Days.
She has had 50 international charting singles over the course of her career, and her songs have helped propel more than 66 albums into the Top Ten of the Billboard 200.
Her songs have been featured in major motion pictures, television shows, film soundtracks, and radio spots, as well as national and international commercial campaigns.
She has written many songs sung by Idol winners and alumni such as Kelly Clarkson, Allison Iraheta, David Archuleta, Carrie Underwood, Diana De Garmo, Katharine Mc Phee, Kris Allen, Danny Gokey, and Adam Lambert.
She co-wrote the American Idol season eight coronation single, "No Boundaries", which was performed by both finalists during the competition.
She wrote "Rebel Hearts" for Hilary Duff's Breathe In Breathe Out album in 2015.
Dio Guardi has also written for films and television series.Dio Guardi wrote and produced "Ooh Ooh Baby" and co-produced "Heaven on Earth" on Spears' album Blackout.Dio Guardi also contributed a majority of songs on Hilary Duff's fourth studio album, Dignity.She wrote "Brand New Day" for Camp Rock 2: The Final Jam, "We Rock" and "Play My Music" for Camp Rock, "He Could Be the One" for Hannah Montana, "Set This Party Off" for Jonas L. and "Someone Watching over Me" for Raise Your Voice.She has also written songs that have been used as themes such as "Taking Chances" on Glee, "Come Clean" on Laguna Beach: The Real Orange County, "Autobiography" on The Ashlee Simpson Show and "Ain’t No Other Man" on Alvin and the Chipmunks: The Squeakquel.In July 2006, Dio Guardi was a judge in an Idol-like TV show called The One: Making a Music Star.