Having made electronic-infused R&B under his real name Jahron Brathwaite [Jahron B], he signed a publishing deal with Warner/Chappell as a songwriter, under the name PartyNextDoor, at age 18. His first mixtape, PartyNextDoor, was released to the iTunes Store on July 1, 2013. It entered on the Billboard Heatseekers Albums chart at number six with sales of 2,000 copies and peaked at number 34 on the Top R&B/Hip-Hop Albums chart for the week of July 20, 2013. He performed background vocals on “Own It” and “Come Thru” from Drake’s third studio album, Nothing Was the Same.

His debut studio album PartyNextDoor Two was released on July 30, 2014. The record featured singles like “Thirsty”, “FWU”, “East Liberty” and the Billboard charted “Recognize”, featuring Drake. Later that year, on December 3, 2014, PartyNextDoor released the 4-track EP titled PNDColours, with the follow up COLOURS 2, released in 2017. In 2015, he produced three songs on Drake’s If You’re Reading This It’s Too Late: “Legend”, “Preach” and “Wednesday Night Interlude”.

PartyNextDoor earned his first number-one song as a songwriter when on January 27, 2016, Rihanna released the lead single “Work” from her eighth studio album, Anti. The song maintained its spot at number-one on the Billboard Hot 100 for nine consecutive weeks. He also penned the song “Sex with Me” on the same album. On March 25, 2016, PartyNextDoor released “Come and See Me”, which features fellow artist Drake, from his upcoming second studio album, PartyNextDoor 3 (also known as P3). A music video directed by affiliate and collaborator Adrian Martinez and featuring appearances by Kylie Jenner, Big Sean, and Jhené Aiko was released on Snapchat on June 23, 2016. On June 15, 2016, Jeremih called into Real 92.3 LA to announce a joint album with PartyNextDoor called Late Night Party. On July 2, 2016, he released another single, “Like That”, featuring Jeremih and Lil Wayne, on OVO Sound radio. On July 21, 2016, PartyNextDoor announced the release date for his second studio album PartyNextDoor 3 for August 12, 2016 and released “Not Nice”, the record’s second single.

He and Jeremih toured in 2016 and had plans to release a joint project.

On June 4, 2017, PartyNextDoor released Colours 2 without any prior announcement. A short film for the EP was released on June 12, 2017.

On September 29, 2017, he released an EP titled Seven Days, which included guest appearances from Halsey and Rick Ross.

On October 15, 2020, Party surprise-announced the release of Partypack, a 7-song EP containing “previously unreleased” songs, including the 2014 song “Persian Rugs”. The EP was released the following day.