VanderWaal began her musical career by posting videos of her original songs and covers on YouTube and performing at open mic nights near her home in Suffern, New York.

In September 2016, at age 12, she won the eleventh season of the NBC competition show America's Got Talent (AGT), performing her original songs.

She has performed at the Planet Hollywood Resort & Casino in Las Vegas, Madison Square Garden, the opening and closing of the 2017 Special Olympics World Winter Games in Austria, various benefit concerts, the Austin City Limits Music Festival and on various television talk shows.

[10] After winning America's Got Talent in 2016, VanderWaal was home-schooled and enrolled in online courses for 7th grade[11][12] but later attended public school[13][14] part of the time.

"[18] She decided to learn the ukulele after watching a Brazilian au pair play and seeing a Twenty One Pilots video on YouTube.

[7] In July 2016, after her audition on AGT, she performed at the Lafayette Theatre in Suffern and then at the Ramapo Summer Concert Series at Palisades Credit Union Park.

[26] On June 7, 2016, VanderWaal auditioned for the eleventh season of NBC's talent competition show AGT, singing her original song about identity, "I Don't Know My Name".

[28] VanderWaal planned to use part of her AGT winnings to make a donation to charity and to buy two tree houses, built by the team from Treehouse Masters, for herself and her sister.

[53] In reviewing the last event, Jon Caramanica of The New York Times commented: "One of the loudest receptions of the night was for Grace VanderWaal, a precociously thoughtful 12-year-old singer-songwriter-ukulele player".

[57] In March 2017, she performed at We Day Illinois at Allstate Arena to celebrate young people's action on social issues.

[58] She also sang "Light the Sky" at the annual benefit gala "One Night for One Drop", organized by Cirque du Soleil at the New York-New York Hotel and Casino in Las Vegas.

[60][61] In April, she performed at WE Day charity events in Seattle,[62] and Los Angeles,[63] and she appeared at the 2017 Radio Disney Music Awards.

[69] By early 2017, VanderWaal began working on a full-length album, eventually titled Just the Beginning, that she called "more produced ... really the same sound ... [but] less acoustic" than her debut EP.

[78] The same month, Windex used VanderWaal's "Beautiful Thing" as the soundtrack to an advertisement,[79] Honda used her cover of "Over the Rainbow" for a Japanese ad,[80] and SheKnows Media ranked "I Don't Know My Name" as one of the 16 most empowering songs for women so far in 2017.

[84] VanderWaal promoted Just the Beginning with performances in September on Ellen[85] and in October at the Austin City Limits Music Festival,[86] where she was "[o]ne of the fest's biggest breakout acts ... whose soaring voice and sweet pop songs charmed large ...

[100] In December 2018, she returned to Live with Kelly and Ryan together with Ingrid Michaelson to perform their duet from Songs for the Season of "Rockin' Around the Christmas Tree".

[110] Courtney Howard, in Variety, commented: "She ropes us into the mystery of her character reveal with heaping amounts of magnetism and grounded authenticity.

[126] Billboard magazine praised VanderWaal's vocals on her debut EP, Perfectly Imperfect, finding them "reminiscent of a Taylor Swift-Regina Spektor hybrid".

[128] Brianna Wiest of Teen Vogue wrote: "The EP takes you through Grace's range, touching on issues that are all-too-well-known for young people, as well as soul-stokingly beautiful medleys that almost anyone could relate to. ...

There's a certain chirp in VanderWaal's voice that's reminiscent of Swift, but otherwise, her vocals align much more closely to Sia's in her full-voiced belting and nonchalant pronunciations.

"[90] A reviewer for The Buffalo News wrote that the "vast diversity in her songwriting ... makes her stand out as a truly unique and exquisite artist.

"[130] Selina Fragassi of the Chicago Sun-Times commented that, on the album, VanderWaal's "raspy-sweet-peculiar vocals recall Elle King, Regina Spektor and Katy Perry ... [and] proves herself a modern-day Mozart".

[131] Critics writing in the Houston Chronicle similarly praised VanderWaal's "smart pop songs that beautifully showcase her persona and wonderfully peculiar rasp of a voice.

"[132] A reviewer for the Dallas Observer opined that VanderWaal's lyrics tackle "complicated issues with aplomb as her raspy, warbling voice undulates around each syllable.

"[133] A reviewer called VanderWaal's Seattle concert in February 2018 "a well balanced set of ballads and full energy songs.

[134] Abby Jones of Billboard wrote that her performance of her single "Clearly" on The Late Show in 2018 was "moving ... stunningly bold ... mature, powerful".

[136] Later that month, a tour reviewer noted, in Argus Leader, "her whimsical flower crown, carefree attitude and incredible voice.

[140] MTV's critic called the 2019 music video for her song "I Don't Like You" "a sharp portrait [that] ... represents the chaos, confusion, and anger we often feel in relationships.

"[114] In 2023, an NBC review said that VanderWaal "has the voice of an angel", called her song "Boyfriend" "deep" and "emotional", and said that her cover of Amy Winehouse's "Wake Up Alone" "sounds heavenly".

[4] In 2019 the New York State Senate awarded her its Women of Distinction honor for her efforts to expand musical education in the East Ramapo Central School District.