The band self-financed their full-length debut, combining the savings of vocalist Tom Araya, who was employed as a respiratory therapist, and money borrowed from guitarist Kerry King's father.

Touring extensively promoting the album, the band brought close friends and family members along the trip, who helped backstage with lighting and sound.

Although the album was criticized for its poor production quality, it became Metal Blade's highest-selling release,[2] producing the songs "The Antichrist", "Die by the Sword" and "Black Magic", which were played at Slayer's live shows regularly.

[2] While performing an Iron Maiden cover, the band was spotted by Brian Slagel, a former music journalist who had recently founded Metal Blade Records.

[2] Recorded in Los Angeles, Show No Mercy was financed by vocalist Tom Araya, who used his earnings as a respiratory therapist,[4] and money borrowed from guitarist Kerry King's father.

[6] Vocalist Araya asserts Venom, Judas Priest, Iron Maiden, and Mercyful Fate were big influences on the record, as guitarist King was into the Satanic image.

As such, Lombardo called Show No Mercy his least favorite Slayer album, although he emphasized that the songs were great, just not his performance.

[8] Gene Hoglan, later known as the drummer for bands like Dark Angel and Death, provided backing vocals on the song "Evil Has No Boundaries".

[11] The band used Satanic themes in both lyrics and live performances to gain notice among the metal community and "to fuck with people".

[12] Due to the imagery and lyrical content, Slayer received mail from the Parents Music Resource Center telling the band to stop releasing records.

"[12] The album produced the songs "The Antichrist", "Die by the Sword", and "Black Magic", which were played at Slayer's live shows regularly.

"[17] The German magazine Rock Hard gave Show No Mercy a positive review, which remarked how Slayer were "actually the hardest and fastest" in comparison with their contemporaries Metallica and Exciter, and defined their music as "heavy metal punk.

[3] Sputnikmusic staff member Hernan M. Campbell described the album as "fast, heavy, and mean, inducing an inescapable atmosphere of utter atrocity."

"[15] Fenriz, drummer for Darkthrone, cited Show No Mercy as the inspiration for the band's "current style of fusing NWOBHM with black metal".

[22] System of a Down's Daron Malakian has praised Show No Mercy as an influential album that helped shape him as a person and artist.