As she said on Rove (Australia) in 2004, she wanted to have more edge to her vocals as she felt there was something missing from her previous works. She brought in many rock instruments which brought a new atmosphere to her music. She also felt that she still needed the funkiness and the pop as the singer felt that too much edge would sound wrong with her voice. Out of this a new sound was formed. She describes her sound as "sprock" - a combination of soul, pop and rock. She named the album after herself. Anastacia entered record studios in September 2003 to begin recording her next album, working with Glen Ballard, Dallas Austin, and Dave Stewart for release in 2004. On the album, Anastacia also collaborated with P.O.D. lead singer Sonny Sandoval on the socially-conscious track "I Do".

The first single, released in March, was "Left Outside Alone", which saw a change in direction for Anastacia. Anastacia proved to be a smash hit reaching the top of the album charts in the United Kingdom, Ireland, the Netherlands, Australia, Greece, Germany, and Italy and number 2 in Portugal and Spain. "Left Outside Alone" proved to be equally successful reaching number 1 in Australia, Spain, Italy, Austria and Switzerland; number 2 in the Netherlands + Germany, number 3 in the UK and reaching the top 5 on the composite European chart. Unlike her first two albums, which were released in her homeland of America, Anastacia was not, despite being scheduled for release on three occasions. "Left Outside Alone" was released twice, but failed to pick up heavy airplay. It only gained sporadic Adult Contemporary and Hot AC format airplay. Again, it sparked Rhythmic/Dance format airplay and the dance mix of "Left Outside Alone" peaked at #1 on the Hot Dance Music/Club Play. After the original version of "Left Outside Alone" failed to catch on because of lukewarm promotional pushes, especially on radio, the album was postponed and eventually cancelled after the release date of August 30, 2004 passed.

Anastacia released three further internationally successful singles; "Sick and Tired" (which gave her another #1 in Spain and another UK Top 5 single), "Welcome to My Truth" (her best-selling hit in Spain), and the ballad "Heavy on My Heart" proceeds from the sale of which went towards her 'Anastacia Fund' (a charitable organization providing research funding for breast cancer). A small batch of Anastacia the album was released with a bonus DVD, Anastacia poster and slip case. The DVD includes "Making Of Anastacia", "2002 Europe Promo Tour" and a photo gallery.

• "Fama ¡a bailar!" (1 episode, 2008)
       - Episode #2.5 (2008) TV episode (performer: "I Can Feel You")
• Premios Principales 2008 (2008) (TV) (performer: "I Can Feel You")
• Divas II (2008) (TV) (performer: "Left Outside Alone" (uncredited), "I Can Feel You" (uncredited))
• "French and Saunders" (1 episode, 2004)
       - Episode #6.5 (2004) TV episode (performer: "I'm Outta Love")
• "Operación triunfo" (2 episodes, 2001-2002)
  ... aka O.T. (Spain: promotional abbreviation)
       - Episode #2.8 (2002) TV episode (performer: "You'll Never Be Alone")
       - Episode #1.6 (2001) TV episode (performer: "Paid My Dues")
• Coyote Ugly (2000) (performer: "Love Is Alive")