She gained recognition for playing Eleven in the Netflix science fiction series Stranger Things (2016–present), for which she received nominations for two Primetime Emmy Awards.

In 2018, Brown was featured in the Time 100 list of the world's most influential people,[2] and was appointed as a UNICEF Goodwill Ambassador, the youngest person ever selected for this position.

In 2014, she had a starring role in the BBC America paranormal drama-thriller series Intruders as Madison O'Donnell.

[12][13] In 2016, Brown was cast to play Eleven in the Netflix science fiction horror series Stranger Things.

[14] She received critical praise for her performance[15] and she was nominated for the Screen Actors Guild Award for Outstanding Performance by a Female Actor in a Drama Series and the Primetime Emmy Award for Outstanding Supporting Actress in a Drama Series.

[23] Brown was chosen to voice in the Darren Aronofsky-produced virtual reality experience Spheres: Songs of Spacetime.

It is available at UK pharmacy Boots, Walmart in the United States and Shoppers Drug Mart in Canada.

[46] In 2024, Brown starred in and executive produced the fantasy film Damsel for Netflix, directed by Spanish filmmaker Juan Carlos Fresnadillo based on a screenplay by Dan Mazeau.

[47] She will next star in the Russo brothers's The Electric State, an adaptation of Simon Stålenhag's graphic novel of the same name.

[51] After Brown turned 18 in February 2022, her social media profiles began to be flooded by sexually explicit material from users.

[56] As of August 2022, she has been an online student at Purdue University Global, studying health and human services.