[6] His great-great-great-grandparents were the American rancher Edwin Dun, who was the United States Ambassador to Japan, and his second Japanese wife, Yama.

[9] He worked at Guitar Center for three years, where he met former Twenty One Pilots drummer Chris Salih, who eventually introduced him to his future bandmate Tyler Joseph.

[10][11] In March 2010, Dun joined House of Heroes after the band's drummer, Colin Rigsby, took a break to spend more time with his family.

[14] After quitting his job at Guitar Center, Dun planned to leave for Nashville, Tennessee in pursuit of a drum career in the industry; however, he was stopped by Twenty One Pilots drummer Chris Salih, who offered him his role.

[15] He went on to play a show with Tyler Joseph after Salih and bassist Nick Thomas left the group due to other commitments.

[17] At this point in Twenty One Pilots' career, the band had topped the charts with their hit single "Stressed Out"–the song's music video being filmed at Dun's childhood home—and has since received over 2.9 billion views on YouTube.

[20][21] The accompanying music video for the track was filmed in both Joseph and Dun's respective homes while they were under lockdown due to the U.S. state and local government responses to the COVID-19 pandemic.

In Dun's directorial debut, he directed the music video for the album's third single, "Backslide", which was released on April 25, 2024.

[34] Some of his earliest purchases were an album by NOFX, and Human Clay by Creed, citing "Higher" as one of his favorite songs.

[34] However, his parents set strict rules on what music he could listen to, about which he later said, "I'd hide albums like Green Day's Dookie underneath my bed.

[38] Dun and Twenty One Pilots bandmate Tyler Joseph both have an "X" tattoo on their body symbolizing their dedication to their hometown fans in Columbus, Ohio.

Dun also sports the name "Tyler" above his left knee, which he received from Joseph onstage during a show at the Eagles Ballroom in Milwaukee, Wisconsin on October 30, 2015.