Bionic initially received mixed reviews from music critics, although in retrospective commentary multiple professional journalists noted it has gained a cult following.

Bionic was promoted in mid-2010 by television performances, such as Aguilera's appearances on The Oprah Winfrey Show, the ninth season of American Idol, Today and MTV Movie Awards.

"[1] After a successful 2006, during which Aguilera released her critically acclaimed and commercially successful fifth studio album Back to Basics, Aguilera received a nomination for a Grammy Award for Best Pop Vocal Album at the 49th Annual Grammy Awards (2007) and won Best Female Pop Vocal Performance for its lead single "Ain't No Other Man".

While on the Asian leg of the Back to Basics Tour, during the summer of 2007, Aguilera said that her upcoming album would be "short, sweet and completely different" from its predecessor.

[3] In a February 2008 interview with People, Aguilera stated that she was going to start recording new material for her forthcoming album at her Beverly Hills, California residence.

"[10] Aguilera set about contacting collaborators on her own accord, at the behest of then-husband Jordan Bratman, without relying on the record label A&R.

During the meeting, Aguilera identified what kind of Ladytron songs she liked, with Hunt later saying: "We were impressed because she had a real deep knowledge of our music – album tracks, not just the singles!".

[38] Mike Usinger from The Georgia Straight opined that the accompaniment of synthesizers on the project "offers up a rise-of-the-fembots strain of robo-pop that sounds like LCD Soundsystem-era Williamsburg.

[39][41][42] Eric Handerson of Slant elaborated that the album "[is] all in service of routine pop sex, the sort of standard-issue sleaze that [...] stood in stark contrast against.

"[43] Echoing Handerson's point of view, The Georgia Straight's Mike Usinger commented: "Where past Xtina efforts have hinted that's she's horny to the core, Bionic makes a concrete case that she's the dirtiest girl working in mainstream pop.

[49] On the song, Aguilera explicitly announces her new persona and style adopted on Bionic,[50] declaring that "The old me's gone I feel brand new / And if you don't like it, fuck you.

[61][45] It begins with "Morning Dessert (Intro)", a soft soul interlude,[39] which describes sex as a daily routine of Aguilera and her husband.

"[41] The next four ballads "Lift Me Up", "All I Need", "I Am", and "You Lost Me" are piano-driven tracks that, in the words of Bent Koepp for Beats per Minute, "have Aguilera showcasing some of her best vocal performances to date.

[66] "Birds of Prey" is an synthpop-influenced[67] electro song backed by "cool" synthesizers,[68] and Aguilera's vocals are delivered in a whispered manner.

[57] It's a mid-tempo electropop ballad, characterized by "a skittering beat filled with beeps, glitches and trills," according to the Billboard magazine.

[72] Ruth Doherty from InStyle called the cover "super-cool" and compared Aguilera's look to that of Arnold Schwarzenegger in the Terminator film series.

[92] Internationally, the song was a moderate commercial success, peaking at number twelve in the United Kingdom,[93] and within the top forty in Australia, Austria, New Zealand and Sweden.

[31] Margaret Wappler of the Los Angeles Times said that Aguilera's "hyper-sexed lover bot" persona is the album's "most successful vein".

[118] Kitty Empire, writing in The Observer, found it to be "very strong, but only in parts", and said that its strength "lies in its core limb-shaking sass, even as it confuses girl-on-girl action with sisterhood.

[119] Slant Magazine's Eric Henderson said that it is as "efficient a pop entertainment" as was Britney Spears' Circus, but felt that its attempt at hedonistic themes "feels synthetic and compulsory.

"[43] Andy Gill of The Independent said that, apart from its basic R&B balladry, the album imitates Spears' and Janet Jackson's "electro-R&B schtick" to disguise Aguilera's "lack of any original approach.

"[34] Jon Pareles, writing in The New York Times, remarked that its musical direction "makes her sound as peer-pressured as a pop singer can be.

[51] Dan Martin of NME said that the occasionally "daring" tracks are marred by ordinary house licks that inhibit Aguilera's singing.

"[122] In similar vein, Mike Wass of Idolator asserted five months later that "the album holds up better than expected, and is actually an intriguing — if somewhat disjointed and often meandering — collection of songs.

"[124] The following October, Joey Guerra of Houston Chronicle echoed these statements regarding the progressive nature of the album, calling Bionic "a forward-thinking assertion of independence like Madonna's 'Erotica' and Janet Jackson's 'The Velvet Rope'.

"[125] One of its tracks, "Birds of Prey", was ranked by Billboard at number 68 on a 2017 list of the hundred best deep cuts by 21st century pop stars, who wrote the song stood out as one of Aguilera's "most sonically beguiling compositions".

[126] Ten years after the record's release, Glenn Rowley of Billboard wrote Bionic had become "something of a cult favorite LP" over time and noted that there had been regular calls for "#JusticeForBionic" — the online campaign — on social media.

[70] Daniel Megarry of the Gay Times shared the same sentiment, calling it a "cult" record among the LGBTQ+ community, and believed it "will likely be re-discovered as a forgotten jewel by pop music fans for years to come".

[137] However, those first-week sales were comparatively less than those of Aguilera's previous studio album Back to Basics (2006), which peaked at number one with 346,000 copies sold.

[157] The album also managed to peak within the top ten in Austria, Belgian region of Flanders, Czech Republic, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Russia, Spain and Sweden.