According to the sheet music published by EMI Music Publishing, "I Wanna Go" is written in the key of D minor, with an electropop beat infused metronome of 130 beats per minute. Spears' vocals range from the low note of D3 to the high note of D5. Critical reception "I Wanna Go" received generally favorable reviews from music critics. A reviewer for Samesame.com.au called "I Wanna Go" Spears' best song since "Toxic", and added that "I’d go so far as to say that it is probably the best song that she has ever recorded. [...] How the decision was made that 'Hold It Against Me' would be a better first single over this is baffling". Parker Bruce of the Washington Square News stated that the song functions as "a sort of formal declaration and mission statement" for Femme Fatale, saying that "It is not an innovative song, but it is fantastically effective and endlessly enticing with its liberating, toss-your-cares-away, dance-like-a-complete–and-utter-fool cathartic chorus, repeated words and typically saucy Britney lyrics". The Daily Collegian writer Hannah Rishel said "I Wanna Go" would have been "another good lead single", while The Washington Timess Andrew Leahey said that along with "Till the World Ends", they are "bass-heavy tributes to club culture." Robert Copsey of Digital Spy called it "anthemic" and noted the song would become a future single. Rich Juzwiak of The Village Voice called "I Wanna Go" the highlight of the album, and said "get ready for [it] to score your summer". However, Juzwiak went on to note that Spears' vocals are heavily manipulated to maximize the chorus's potential, even though "the joy she sings about is palpable". The Chicago Sun-Times journalist Thomas Conner also noted that the singer's vocals were processed to the point "these songs could be sung by anyone", exemplifying I Wanna Go' tweaks her up so high she could be Jackie Evancho". Andy Gill of The Independent also criticized the singer's vocals on Femme Fatale, stating that they sounded more programmed than natural, with "even the little whistling hook in 'I Wanna Go' has a synthetic character about it". Sal Cinquemani of Slant Magazine noted that "If not for its infectious pre-chorus whistle, 'I Wanna Go' would be just another song off the Max Martin assembly line". The Guardian contributor Alexis Petridis gave the song a negative review, and said that although most of tracks of the album are