Her appearances on various TV shows led to her first prime-time role as Tiffany Malloy on the sitcom Unhappily Ever After, which ran on The WB from 1995 to 1999 for a total of five seasons. Her brother Matthew guest-starred on a handful of episodes, including one where he wore a "Ghostface" mask (the type of mask featured in Scream).
After Unhappily Ever After was cancelled (she appeared in all 100 episodes), Cox went on to portray Taylor Clayton, a former call-girl turned social worker on the ABC television sitcom The Norm Show which lasted for three seasons (she appeared in 27 of its 54 episodes). Next she starred as Nikki White in Nikki, another sitcom vehicle that lasted for two seasons on The WB (2000–2002).
The most successful show Cox co-starred in following her time on Unhappily Ever After was on the NBC TV drama Las Vegas from 2003 to 2007 for a total of four seasons. She played Mary Connell for 88 episodes. However, Cox would not appear on the fifth and final season of the show. On May 20 and 23, 2005, her Las Vegas character crossed over to NBC's soap opera Passions to coincide with the arrival of two new characters introduced on Las Vegas.
On December 29, 2006, she married comedian/actor Jay Mohr in Los Angeles.[4] The two met on the set of Las Vegas.[5] In December 2008, Mohr petitioned a Los Angeles court to allow him to legally add her last name to his, changing his name to Jon Ferguson Cox Mohr.[6] Cox and Mohr have a son. On the May 16, 2017, episode of The Adam Carolla Show, Mohr confirmed that he and Cox were "in the middle" of a divorce.[7] Their divorce was finalized in August 2018.[8]