Writing for MTV Buzzworthy, Nicole James complimented the track for its successful blending of "super early Madonna" and "21st-century synthpop", and drew similarities to the music of artists such as Chromeo, La Roux, and Robyn.

; he directed his praise towards its "blippy, skittering electronica beats and a big fat slapping bass", while additionally noting its apparent inspiration by pop singer Britney Spears.

[10] A writer for Idolator expressed excitement that Ferreira continued pursuing her musical endeavors after her earlier cover version of "Animal" by Miike Snow.

[11] Writing for Rolling Stone, Colleen Nika was confident that "Sex Rules" introduced a "spiky" sound that could become popular in the evolving contemporary hit radio market.

[4] However, The New York Times' Jon Caramanica opined that the "dry" vocal performance made it difficult for Ferreira to meaningfully deliver the lyrics.