[11] Nowels co-wrote and co-produced the hit single "The Game of Love", performed by Santana and Michelle Branch, which won ASCAP Song of the Year in 2003.

Nowels co-wrote and co-produced the hit single "Out of Love"[12] with Alessia Cara from her sophomore album, The Pains of Growing.

In collaboration with R&B singer-songwriter Miguel, Nowels co-wrote the hit single "Lost in Your Light" for Dua Lipa's self-titled debut album.

Nowels co-wrote the hit single "Loud Places" from In Colour, the solo debut album of Jamie xx.

The same year, Nowels co-wrote five songs for Tom Odell's third album, Wrong Crowd,[17] along with the hit single, "Magnetized".

[18] Together, they wrote "The Power of Good-Bye",[19] "Little Star" and "To Have and Not to Hold", all featured on Madonna's seventh studio album, Ray of Light.

[20][21] Ray of Light won Best Pop Album at the 1999 Grammy Awards, where Madonna thanked Nowels from the stage during her acceptance speech.

[28] In a three-day writing session they composed "Summertime Sadness", "Dark Paradise", "Lucky Ones", and "TV in Black & White".

[33][34] In 2013, Nowels and Del Rey's song, "Young and Beautiful", was featured in Baz Luhrmann's film, The Great Gatsby.

Del Rey and Nowels co-wrote 14 of the songs for the album including the 3 singles, "Love", "Lust for Life" (featuring the Weeknd), and "White Mustang".

[40][41][42] Nowels co-wrote "Lost in Your Light", recorded by Dua Lipa featuring Miguel, which was released on 21 April 2017 as the sixth single from the former's self-titled debut studio album.

Nowels is a supporter of TreePeople Los Angeles, The Sierra Club, and the Natural Resource Defense Council (NRDC).