Myleene was a member of the pop group Hear'Say, and later released two solo classical crossover albums in 2003 and 2007.
In 2001, Klass auditioned for the ITV reality show Popstars, which offered contestants an opportunity to become part of a newly formed pop band. Klass was chosen as one of the ten finalists and became a member of Hear'Say, with Kym Marsh, Suzanne Shaw, Danny Foster and Noel Sullivan. Following the success of their first album, the band was given its own TV show entitled Hear'Say It's Saturday. During the show's run, the band had a chance to perform with such established artists as Lionel Richie, Celine Dion, Bradley Walsh, Blue and Atomic Kitten. At the end of 2001, Hear'Say appeared on the Royal Variety Performance.
On 13 May 2003, Klass signed a five-album deal with Classics and Jazz. Promotion started with the release of the main promotional single "Toccata and Fugue" to TV channels. She also appeared in the video for "Da Ya Think I'm Sexy?" with The Girls of FHM, which went to No. 10 in the UK Singles Chart.
Klass's album, Moving On, was launched on 20 October 2003 at Harrods, London. The album included reworked versions of popular classical pieces such as Fauré's Pavane, Beethoven's Moonlight Sonata and Satie's Gymnopedie No.2. Moving On also included music from the Oscar-winning films Gladiator and The Piano.
On 28 March 2007, Myleene Klass signed a record contract with EMI Classics as both a recording artist and an ambassador for the EMI Classics UK roster of artists. These include Alfie Boe, Natasha Marsh and Natalie Clein. The deal included the release of a series of albums on which Klass performed two exclusive tracks and chose a number of her favourite classical pieces from the EMI Classics back catalogue.
On 6 August 2006, Klass was a guest reporter on BBC One's Sunday morning religion and ethics show, Heaven & Earth, with Gloria Hunniford. Klass's report, billed as the feature of the week, was on the Pope's astronomer. From 10 October 2006, Klass co-presented Living's Ghost Towns with the medium and ex-Most Haunted star Derek Acorah. In May 2007, Klass appeared on Sky HD's Test Card.
From July to August 2007, Klass co-presented the daily BBC One programme The One Show with Adrian Chiles, before leaving to concentrate on looking after her baby. On 31 December 2007, Klass presented the BBC One programme, New Year Live, for the countdown to the year 2008 at midnight.
Myleene Klass was announced as the new presenter of the Channel 4 series 10 Years Younger, on November 5, 2008, and first hosted on February 5th of the following year. The programme was broadcast every Thursday evening, from 9.00 pm to 10.00 pm. Klass replaced Nicky Hambleton-Jones as presenter. She also co-hosted the American version of I'm a Celebrity... Get Me out of Here! in 2009 on NBC.
On 31 July 2015, Klass began presenting the new ITV series BBQ Champ.