Black Sabbath is included in Robert Dimery's 2005 musical reference book 1001 Albums You Must Hear Before You Die.

According to Black Sabbath's guitarist and founding member Tony Iommi, the group's debut album was recorded in a 12-hour session on 16 October 1969.

"[11] Aside from the bells, thunder and rain sound effects added to the beginning of the opening track and the double-tracked guitar solos on "N.I.B."

"[12] The key to the band's new sound on the album was Iommi's distinctive playing style that he developed after an accident at a sheet metal factory where he was working at the age of 17 in which the tips of the middle fingers of his fretting hand were severed.

In the same article, bassist Geezer Butler added, "Back then the bass player was supposed to do all these melodic runs, but I didn't know how to do that because I'd been a guitarist, so all I did was follow Tony's riff.

Still, a malfunctioning pickup forced him to finish recording with a Gibson SG, a guitar he had recently purchased as a backup but had "never really played."

In his autobiography Iron Man: My Journey Through Heaven & Hell with Black Sabbath, Iommi plays down the producer's role, insisting, "We didn't choose to work with Rodger Bain, he was chosen for us...

[13] In retrospect, AllMusic's Steve Huey feels that Black Sabbath marks "the birth of heavy metal as we now know it".

[14] Huey notes the first side's allusions to themes characteristic of heavy metal, including evil, paganism, and the occult, "as filtered through horror films and the writings of J. R. R. Tolkien, H. P. Lovecraft, and Dennis Wheatley.

[15] In his opinion, the album represented a transition from blues rock into "something uglier", and that this sound "found deeper gravity via mournful singing and a sinister rhythmic pulse".

[15] According to Rolling Stone magazine, "the album that arguably invented heavy metal was built on thunderous blues-rock".

[19] Taking a broader perspective, Pete Prown of Vintage Guitar says, "The debut Black Sabbath album of 1970 was a watershed moment in heavy rock, but it was part of a larger trend of artists, producers, and engineers already moving towards the sound we now call hard rock and heavy metal."

[18] In the liner notes to the band's 1998 live album Reunion the bassist remembers: I'd been raised a Catholic so I totally believed in the Devil.

[21] Contrary to popular belief, the name of that song is not an abbreviation for "Nativity in Black;"[8] according to Osbourne's autobiography it is merely a reference to drummer Bill Ward's pointed goatee at the time, which was shaped as a fountain pen-nib.

In his autobiography, Iommi admits the band reluctantly agreed to do the song at the behest of their manager Jim Simpson, who insisted they record something commercial.

Standing in front of the watermill is a figure dressed in a black cloak, portrayed by model Louisa Livingstone, whose identity was not widely known until 2020.

[24] "I'm sure (McMillan) said it was for Black Sabbath, but I don't know if that meant anything much to me at the time," Livingstone recalled, adding that it had been "freezing cold" during the shoot.

[25] According to McMillan, Livingstone was wearing nothing underneath the black cloak, and some experimentation was done involving some "slightly more risqué" photographs taken at the session.

"[25] The inner gatefold sleeve of the original release featured an inverted cross containing a poem written by Roger Brown, McMillan's photography assistant.

[27] "I got a call from a guy, Olav Wyper, at a newly-set-up label, Vertigo," recalled Sabbath manager Jim Simpson.

[29] Following its United States release in June 1970 by Warner Bros. Records, the album reached number 23 on the Billboard Top LPs chart,[30][31] where it remained for more than a year and sold one million copies.

Huey was also impressed by how the band's "slowed-down, murky guitar rock bludgeons the listener in an almost hallucinatory fashion, reveling in its own dazed, druggy state of consciousness".

"[40] In the opinion of Mike Stagno of Sputnikmusic, "both fans of blues influenced hard rock and heavy metal of all sorts should find something they like on the album.

"[43] In Mick Wall's book Black Sabbath: Symptom of the Universe, Butler reflects, "The London press absolutely hated us when we made it 'cos they'd never written an article about us, they didn't know of us.

[48] Rolling Stone ranked Black Sabbath number 44 in their list of the 100 Best Debut Albums of All Time, describing the title track as the song that "would define the sound of a thousand bands".

The original North American Warner Bros. Records pressings of Black Sabbath list incorrect running times for "Wicked World" and the "Warning" medley (4:30 and 14:32, respectively), and also credit the album's original songs using the band members' given names (Anthony Iommi, John Osbourne, Terence Butler, and William Ward).