Alongside being a child actor, he's also a child voice actor. Aside from We Bare Bears, Duncan has also voiced as a character named Ian in Disney Jr.'s series Doc McStuffins.
- The only two animated series Duncan has been credited for voicing in are We Bare Bears and Doc McStuffins.
- Duncan only voiced Ian in one episode of Doc McStuffins, while all other times the character was voiced by someone else.
- Duncan Joiner has always voiced Baby Panda in every Baby Bears episode until Lil' Squid because he's replaced by another child actor and is now voiced by Max Mitchell due to his departure and has probably outgrown his role or maybe they're however taking turns voicing Baby Panda.
|Voice actors||Bobby Moynihan • Charlyne Yi • Demetri Martin • Duncan Joiner • Edi Patterson • Eric Edelstein • Estelle • Jason Lee • Keith Ferguson • Niki Yang • Patton Oswalt • Rodger Bumpass • Sam Lavagnino|
|Show staff||Abe Audish • Brad Breeck • Brian A. Miller • Bert Youn • Charlie Parisi • Christina Chang • Curtis Lelash • Daniel Chong • Danny Ducker • Guillermo Martinez • Jennifer Pelphrey • Kyler Spears • Lauren Sassen • Lilit Atshemyan • Louie Zong • Madeline Sharafian • Manny Hernandez • McKenna Harris • Mikey Heller • Nate Funaro • Nooree Kim • Randy Myers • Rob Sorcher • Sarah Sobole • Tara Helfer • Teresa Hsiao • Tom Law • Violet Bruce|
|Guests||Adam Campbell • Dia Frampton • Ellie Kemper • Eric Favela • Suzie Vlček • Phil Rynda • Sue Mondt • Vera Brosgol|