|The following is a list of main and recurring characters in the Blue's Room series.
- Blue is an outgoing plush puppet who loves to talk. She is puppeteered by Leslie Carrara-Rudolph and voiced by Victoria Pontecorvo.
- Polka Dots is Blue's best friend, who often gives his friends puzzles to solve. He is puppeteered by Peter Linz.
- Fred is a princess doll who likes to pretend that it is her birthday every day of the year. She is puppeteered by Cheryl Blaylock.
- Roary is a fun-loving stuffed dinosaur who, as his name implies, roars often. He is puppeteered by Joey Mazzarino.
- Sprinkles is Blue's younger brother introduced in the "Meet Blue's Baby Brother!" episode. He is puppeteered by Joey Mazzarino.
- Doodleboard is an art easel who often asks Blue and the viewer to guess what he is drawing. He is puppeteered by Peter Linz.
- Dress-Up Chest is a purple treasure chest who provides Blue and friends costumes to wear. He is puppeteered by Tyler Bunch.
- Boogie Woogie is a jukebox who plays music for the characters to sing and dance along to. He is puppeteered by Joey Mazzarino.
- Silly Seat is a joke-telling chair who appears only in the first season. He is puppeteered by Marc Petrosino and voiced by Jared Goldsmith.
- Joe is Blue's human caretaker, who becomes a recurring character in the second season. He is portrayed by Donovan Patton.
- Moona is an animated fairy who recites the line "Time to go, Blue!" at the end of many episodes. She is voiced by Christiana Anbri.
- Journal is an animated notebook whose features are similar to those of Polka Dots. He is voiced by Brianna Gentilella.
- Key is the key that unlocks Blue's room. He is kept in Polka Dots' back pocket, and is voiced by Jared Goldsmith.
- Antonio is a good friend of Blue. He is one of two human characters to make multiple appearances in the series, and is portrayed by Antonio Ortiz.