Cat Deeley's left full time modelling in 1997, and became an MTV UK presenter, usually with Edith Bowman. From 1998 until 2002, she was host with Ant & Dec on the Saturday morning children's programme SMTV Live and hosted its spin-off programmes CD:UK (1998 -2005) and CD:UK Hotshots. In 2001, she won a Children's BAFTA award for best presenter and appeared in an episode of the BBC's Happiness. In 2002, Deeley appeared in a television advert for Marks and Spencer. Other programmes she hosted include The Record of the Year, Fame Academy, The 2004 BRIT Awards and Stars in Their Eyes, as well as a weekly broadcast on London's Capital FM and BBC Choice series Roadtripping both with former MTV colleague Edith Bowman. In 2003 she became patron of Great Ormond Street Hospital, and in 2005 she played herself in an episode of Little Britain and provided the voice of "Loretta Geargrinder" in the UK version of the film Robots, replacing Natasha Lyonne.

Since 2006, she began the second series of American reality show So You Think You Can Dance, replacing Lauren Sanchez, who was pregnant. Deeley interviewed Kylie Minogue for a television special which was broadcast in the United Kingdom on Sky One on 16 July 2006, in Australia on Channel Nine on 17 July 2006 and BBC America on 9 September 2006. Deeley was guest reporter on NBC's Tonight Show. She has presented Fox's New Year's Eve special from Times Square in 2006 and 2007. She is an entertainment contributor for ABC News, covering awards ceremonies including the Golden Globes and the Grammy and Academy Awards. In 2007, she presented the UK coverage of the sixth series of American Idol for ITV2. She filmed segments and interviews with guests and eliminated contestants for UK audiences that were shown just before and after advertising breaks. However, this was not popular with viewers who saw Deeley's role as 'unnecessary'. She did not return for the seventh series American Idol in 2008.

Deeley was the face of Shape Water and a number of Garnier Fructis products, appearing in print and television advertising in the UK and Ireland. On 1 July, 2007, Deeley was one of many speakers at the Concert For Diana. The event, watched by an estimated 500 million, was at the new Wembley Stadium. In September 2007, Deeley presented "Soundtrack To My Life" an insightful and thought-provoking music series produced by Hamma & Glamma Productions for ITV London that looks at the work and influences of an eclectic band of musicians. In January 2008, a new series of So You Think You Can Dance started its auditions, with Deeley again hosting. In March 2008, Deeley presented the third series of "Soundtrack To My Life", once again produced by Hamma & Glamma Productions for ITV London. On 12th October 2008, Deeley played herself as host of Peter Kay's Britain's Got The Pop Factor ... And Possibly A New Celebrity Jesus Christ Soapstar Superstar Strictly On Ice. On the week of February 16-20, 2009, Deeley guest hosted the syndicated version of Who Wants to Be a Millionaire, replacing Meredith Vieira. On April 10, 2009, Deeley appeared on BBC America's broadcast of "Gordon Ramsay's F Word."

• Britain's Got the Pop Factor ...and Possibly a New Celebrity Jesus
  Christ Soapstar Superstar Strictly on Ice (2008) (TV) .... Herself
  ... aka Peter Kay's Britain's Got the Pop Factor ...and Possibly a New
  Celebrity Jesus Christ Soapstar Superstar Strictly on Ice (UK: promotional title)
• 2008 Primetime Creative Arts Emmy Awards (2008) (TV) .... Herself
• "So You Think You Can Dance" .... Herself - Host / ... (57 episodes, 2005-2008)
       - Results Show: Winner Announced (2008) TV episode .... Herself - Host
       - The Top Four Perform (2008) TV episode .... Herself - Host
       - Results Show: Two Dancers Eliminated (2008) TV episode .... Herself - Host
       - The Top Six Perform (2008) TV episode .... Herself - Host
       - Results Show: Two Dancers Eliminated (2008) TV episode .... Herself - Host
        (52 more)
• "Live with Regis and Kathie Lee" .... Herself (1 episode, 2008)
  ... aka "Live with Regis & Kelly" (USA: new title)
  ... aka "Live with Regis" (USA: new title)
       - Episode dated 10 June 2008 (2008) TV episode .... Herself
• The Big Match (2008) (TV) .... Herself - Host
• Bones: Access All Areas (2008) (TV) .... Herself
• "Entertainment Tonight" .... Herself (1 episode, 2007)
  ... aka "E.T." (USA: informal title)
  ... aka "ET Weekend" (Australia: weekend title)
  ... aka "Entertainment This Week" (weekend title)
  ... aka "This Week in Entertainment" (USA: weekend title)
       - Episode dated 31 December 2007 (2007) TV episode .... Herself
• New Year's Eve Live (2007) (TV)
• Concert for Diana (2007) (TV) .... Herself - Presenter
• "The F Word" .... Herself (1 episode, 2007)
  ... aka "Gordon Ramsay's F Word" (UK: promotional title)
       - Episode #3.8 (2007) TV episode .... Herself
• Secrets of Celebrity Stars in Their Eyes (2007) (TV) .... Herself
• "The Late Late Show with Craig Ferguson" .... Herself (2 episodes, 2006-2007)
       - Episode dated 23 May 2007 (2007) TV episode .... Herself
       - Episode #2.165 (2006) TV episode .... Herself
• New Year's Eve Special (2006) (TV) .... Herself - Host