David Renshaw of
Gigwise gave "Headlock" four out of five stars, writing that it was "a fantastically quirky pop song" and praising it for its "twists, turns and slides". In a review of
Speak for Yourself for
Under the Radar, Nick Hyman wrote that "Headlock" "sets the tone fantastically" for
Speak for Yourself. Luerssen of AllMusic wrote that "Headlock" was one of the album's songs that "suggest[s] Heap has written and produced the finest electro/alt rock CD of 2005". In a 2012
YouGov survey of more than five thousand of Heap's fans, 26 percent named "Headlock" as their favourite song of Heap's, making it her fourth most-favoured song by fans at the time after "
Hide and Seek", "Let Go" by
Frou Frou, and "
Goodnight and Go". "Headlock" debuted at number 74 on the
UK Singles Chart for the week dated 22 October 2006. Upon its release, Heap requested to have it added to
BBC Radio 1's rotation, but was told by the station that, since they already had
Nerina Pallot on their playlist, they did not need another female singer-songwriter. "Headlock" became popular on
TikTok starting in October 2024, initially due to its use in video tributes to the horror video game
Mouthwashing. It had been used in more than 135 thousand videos on the platform by January 2025. Michael Savage of
The Guardian also attributed its success to an increase in nostalgia for music and television series from the 2000s on the platform. That month, due to its increased popularity on streaming services, it became Heap's first career entry on the
Billboard Hot 100 chart, debuting at number 100, and debuted on the
Canadian Hot 100, also at number 100. It became her highest-charting and first top-40 entry on the UK Singles Chart, peaking at number 30 in February 2025. ==Other appearances==