In 1997, de Matteo opened Filth Mart, an East Village clothing store with her then-boyfriend Michael Sportes. They closed the store in 2004.
From 2004 to 2006, de Matteo portrayed Joey Tribbiani's sister Gina in the Friends spin-off Joey. The show was cancelled after two seasons.
After graduating from the Loyola School, she studied at New York University's Tisch School of the Arts, originally hoping to become a Director, not an Actress. De Matteo's role in The Sopranos was one of her earliest, helping to launch her career. She has appeared in several films including Swordfish, Deuces Wild, The Perfect You, Prey for Rock & Roll and the 2005 remake of John Carpenter's 1976 action film Assault on Precinct 13. She had the starring role in Abel Ferrara's R Xmas for which she received some very positive reviews.
De Matteo played the role of Wendy Case in the FX original series Sons of Anarchy. The pilot episode aired September 3, 2008, and De Matteo continued making regular appearances into the series' sixth season. She was promoted to a series regular for the seventh and final season.
De Matteo started dating musician Shooter Jennings in 2001. They became engaged on June 11, 2009, when Jennings proposed onstage at the Stanley Center during a show in Utica, New York. They have two children together, daughter Alabama Gypsyrose Jennings (born November 2007) and son Waylon Albert "Blackjack" Jennings (born April 2011). Jennings and de Matteo eventually ended their relationship without marrying. In July 2015, de Matteo became engaged to Whitesnake bass Guitarist Michael Devin.
De Matteo played Angie Bolen, the mother of the Bolen family, on season 6 of the ABC show Desperate Housewives. She officially left Desperate Housewives at the season 6 finale in 2010, due to personal reasons.
De Matteo lost her apartment home of 22 years, as did dozens of other residents, when a gas explosion and raging fire destroyed three New York City buildings on March 26, 2015.
De Matteo played the stepmother of Steve Wilde, the main character of the FOX comedy Running Wilde, appearing in Season 1, Episode 9. De Matteo co-starred as Krissi Cates in the film adaptation of Dark Places (2015), with Charlize Theron, Chloë Grace Moretz, and Nicholas Hoult. In 2015, she was cast as Det. Tess Nazario in the NBC drama series Shades of Blue, starring alongside Jennifer Lopez and Ray Liotta. It premiered on January 7, 2016.