Her music career began at the age of 15, when she auditioned for The X Factor UK on three occasions before rising to prominence as a member of the girl group Little Mix.

[2] She identifies herself as mixed-race,[3] and has been learning to connect more with her Arab-Egyptian-Yemeni heritage and its language in hopes of travelling more to the Middle East.

[2][3] During her teenage years, she studied pop vocals and cosmetic makeup and completed three A-levels at South Tyneside College.

[4] In 1943, Thirlwall's grandfather Mohammed Ahmed Saleh Badwi, a devoted Muslim, emigrated to South Shields, from Yemen, and worked as a fireman in the merchant navy, and as a labourer at the docks.

[2][5] In 2008, at the age of 15, Thirlwall auditioned for The X Factor (UK), singing "Where Do Broken Hearts Go" by Whitney Houston,[6] but was eliminated at the boot- camp stage.

[8] In 2011, at age 18, Thirlwall returned for the show's eighth series and auditioned with "I Want to Hold Your Hand" by the Beatles, and advanced to bootcamp stage.

Without a performance, they automatically progressed to the judges' houses and reached the live shows where they were mentored by Tulisa Contostavlos.

[31] On 25 October, she performed "Fantasy" and a cover of Chase & Status and Stormzy's "Backbone" on BBC Radio 1's Live Lounge.

[34][35] Thirlwall performed "Fantasy" and a medley of Donna Summer's "Hot Stuff" and Eddie Floyd's "Knock on Wood" on Jools' Annual Hootenanny on 31 December 2024.

[37] She received nominations for Best Pop Act and Song of the Year ("Angel of My Dreams") at the 2025 Brit Awards, and will perform at the ceremony.

[54]Since 2020, Thirlwall has been in a relationship with English singer Jordan Stephens, from the hip hop duo Rizzle Kicks.

The pair started dating in 2020 and were spotted together for the first time at a Black Trans Lives Matter rally in central London in July of that year.

Thirlwall is open about her struggles with body image, racism, bullying, and eating disorder, which she first developed at that age of 13.

[59] In 2020, she was featured in a documentary titled Leigh-Anne: Race, Pop & Power, and spoke about the time that she wanted cosmetic surgery after discovering her images were heavily edited to make her look as "white as possible" during her earlier days in Little Mix.

[60] In 2022, Thirlwall appeared on Heat magazine's "UK and Ireland 30 under 30" rich list for the first time with an estimated net worth of £17.5 million placing her at number 15.

[65] In June 2020, she collaborated with Skinnydip London, a British clothing brand, with the money from her collection being donated to help struggling families in South Shields.

[67][68] In September 2020, she was photographed alongside Heidi Klum, Lil Nas X and Helen Christensen by fashion campaign Christian Cowan for his Spring/Summer 2021 collection.

[74] She is noted for her political reviews and social activism, advocating for LGBTQ+ rights and Black Lives Matter and against transgender conversion therapy in the UK.

[89] In July 2021, she signed an open letter to the UK Equalities minister Liz Truss calling for a ban on all forms of LGBT+ conversion therapy.

[91] She also teamed up with a designer to create a limited edition community shirt for a North East football club, with all donations going to charity Cancer Connections.

[92] Thirlwall attended the Not Safe To Be Me protest at Downing Street advocating for the ban on transgender conversion therapy in the UK, following the government's reversal on the issue.