Born in Astoria, Queens, and raised in Baldwin, New York, Martinez rose to fame in 2012 after appearing on season 3 of the American television talent show The Voice.

[2] Martinez later released her debut studio album, Cry Baby (2015), which went on to be certified double platinum by the Recording Industry Association of America (RIAA).

Known for her colorful two-toned hair and bangs, Martinez's visual style plays an important part in her music videos and performances.

[14][16][17][18] Martinez grew up in a "traditional Latin household" where she was made to feel shameful about talking about her sexuality and felt as if she would not be accepted if she came out as bisexual.

Several months after the initial audition, while at Roosevelt Field Mall, Martinez received word that she had advanced to the "second round".

[9] Martinez auditioned singing Britney Spears's "Toxic" with three of the four judges (Adam Levine, CeeLo Green and Blake Shelton) hitting their "I Want You" button.

Levine eliminated James, and Martinez moved on to the Live Rounds as one of the five remaining members of Team Adam.

[27] Martinez was eliminated by audience vote in week five, along with the fellow Team Adam member Amanda Brown, leaving Levine with no artists.

[34][35][36] The only single from the EP, "Carousel", reached number nine on the Alternative Digital Songs chart, was certified gold by the RIAA, and featured in a preview for FX's miniseries American Horror Story: Freak Show.

[57] On December 22, 2017, Melanie Martinez released the song "Piggyback" on SoundCloud, believed to reflect on allegations made by her former friend, Timothy Heller.

[67] The album was promoted with the K–12 Tour began on October 13, 2019, in Washington, D.C. and concluded prematurely on February 17, 2020, in Brixton, England due to the COVID-19 pandemic.

[68] In January 2020, Martinez announced she was working on an EP titled After School, which was then set to be released in the spring of 2020 and serve as the deluxe edition of K–12.

[76] The album was released on March 31, 2023, and was promoted with the singles, "Death" and "Void" which charted at number 95 and 61 respectively, marking her first original appearances on the Billboard Hot 100.

The collection launched in a sculptural vessel modeled after Martinez's four eyed "Cry Baby" alter ego which houses all four fragrances and retails for $275.

[80] Since the release, a further three music videos have appeared, one featuring the song "Tunnel Vision" in December 2023,[81] a second in February 2024 for "Faerie Soirée",[82] and a third in May 2024 for "Light Shower".

[18] The New York Times's Jon Pareles described her music as "perch[ing] prettily tinkling keyboards and concise pop choruses amid the slow, ominous basslines and twitchy percussion of Southern hip-hop – a candy-coated variation on the dirges of Lorde and Lana Del Rey", and described her mezzo-soprano voice[95][96] as "whispery, sardonic, tearful, [and] furious".

[98] Martinez describes her alter ego and the protagonist of her debut album, Cry Baby, as a "fairy tale" version of herself.

[101] Martinez listened to Christina Aguilera, Brandy, Britney Spears, The Beatles, Tupac Shakur, Shakira, and Biggie Smalls growing up,[102][84][103] and wanted to be a singer from a young age.

[104] Martinez has cited The Beatles,[105] Neutral Milk Hotel, Feist, Kimbra,[9] Zooey Deschanel, Regina Spektor,[24] and CocoRosie as influences of hers.

[21][108] At age sixteen, after watching 101 Dalmatians (1996), Martinez dyed half of her hair blonde, in the same vein as Cruella de Vil.

[110] The Guardian has called her image "doll-like and decidedly emo [...] hyperreal" while her music is best known to be "part-nursery rhyme, part tragic life story".

[118] She also described harassment she experienced from Martinez's fanbase, stating that she "suddenly had thousands of hate accounts dedicated to [her], thousands of dislikes and negative comments on all of [her] music, and completely ridiculous fabricated stories of [her] being posted online" that ultimately led her to temporarily deactivate her public accounts.