Upon release, "Not My Baby" was met with universal acclaim from music critics. While Idolator's Mike Wass concluded that the song was an "instantly endearing banger" that could attain commercial success, CelebMix's Jonathan Currinn called it one of Inna's best releases in recent memory, by April 2020. Also noting the high remix potential, the latter reviewer pointed out that while Inna had taken musical inspiration from her older releases, the deep house elements in the track were nonetheless an unexplored field for her. Aficia writer Valentin Mafroy saw "Not My Baby" as "modern" and effective", furthermore jokingly stating that the song lyrically contradicted with its predecessor, "Bebe" (2019), where Inna sang about holding on to her partner.
