Born in Guildford and raised in Los Angeles, she began performing on screen at the age of two in the BBC sitcom Growing Pains.

In the late 2000s, she began acting and modelling more regularly, and gained recognition for her supporting role in the sports drama film The Blind Side (2009).

[2] Her maternal grandfather was a Canadian Jewish immigrant who for many years owned a men's clothing store in Beverly Hills, California.

Robbie Collin from the British newspaper The Daily Telegraph wrote of her: "She has an adorable, sensational, almost perfect face for cinema; think Audrey Hepburn with the eyebrows of Liam Gallagher.

"[30] Collins had a leading role as aspiring actress Marla Mabrey in the romantic comedy-drama Rules Don't Apply (2016).

[32] In March 2016, Collins joined the anorexia drama film To the Bone in the lead role, written and directed by Marti Noxon.

"[37] Justin Chang of Los Angeles Times wrote that "In a different film, Ellen's sharp tongue might have made her an insufferable fount of wisecracking negativity, but Collins' performance is subtler than that, and the script gives her ample opportunity to reveal the character's more complicated, vulnerable edges.

[44] In 2017, it was revealed that Les Misérables would be adapted by Andrew Davies into a BBC mini series directed by Tom Shankland.

[45] Collins starred as Fantine, a young woman in Paris who is abandoned by her wealthy lover, forcing her to look after their child, Cosette, on her own.

"[48] In 2019, Collins co-starred with Zac Efron in the drama Extremely Wicked, Shockingly Evil and Vile, directed by Joe Berlinger.

[54] For Emily in Paris, Collins received a second Golden Globe Award nomination for Best Actress – Television Series Musical or Comedy.

[55] That same year, she portrayed Rita Alexander, an English transcriber to writer Herman J. Mankiewicz, in the critically acclaimed film Mank.

[58] In June 2021, it was announced that Collins would produce a film to be directed by Lena Dunham about the children's toy Polly Pocket.

[62] She was selected by Chanel to wear one of their gowns at the 2007 Bal des débutantes at the Hôtel de Crillon in Paris, which was featured on season three of the reality television series The Hills.

[69] Since 2018, she has also been an ambassador for the GO Campaign, a nonprofit organisation that raises awareness and funds to improve the lives of orphans and vulnerable children around the world.

[70] Collins stated in 2013 that she did not like to discuss her relationships publicly after witnessing the difficulties caused by the media coverage of her parents' divorce.