In January 2017, she won a People's Choice Award for "Favorite YouTube Star". In September 2017, Singh won her fourth Streamy Award.
Her first book, How to Be a Bawse: A Guide to Conquering Life, was released on March 28, 2017. The book reached No. 1 on the New York Times bestseller list. She won the award for Best Non- Fiction at the 2017 Goodreads Choice Awards. Her 2017 world tour was centered around the book release and key concepts she discussed.
Singh was cast in HBO's film adaptation of Fahrenheit 451 after recording an audition outside an Internet café in Melbourne, Australia. She was in the region to promote her book and rushed the audition at her agent's urging around 2 a.m. in May 2017. She plays the character of Raven, "a tabloid blogger who works with the fire department to spread the ministry's propaganda by broadcasting their book-burning raids to fans".
In October 2017, she hosted SlutWalk, an initiative started by Amber Rose.
In November 2017, Lilly Singh was also chosen as an ambassador for Pantene shampoo and partnered with Calvin Klein. In 2018, Singh appeared in the music video for Maroon 5's "Girls Like You" featuring Cardi B.
In 2017, Lilly Singh was announced as a UNICEF Goodwill Ambassador, to advocate for children's rights. She has led a campaign called "GirlLove", promoting girls to end girl-on-girl bullying. In July 2018, Lilly travelled to South Africa as a UNICEF Goodwill Ambassador to meet the students of elementary schools who spoke against bullying and classroom violence.