Canada and PBS Kids in the United States on November 26, 2014, both on the same day. The series is co-produced by The Fred Rogers Company and Sinking Ship Entertainment in association with TVOKids and Ici Radio-Canada Télé. The series is created by Tim McKeon and Adam Peltzman.
- Agent Olive (Dalila Bela) - A young veteran agent of Odd Squad, Olive is adapting to working with and training her new partner, rookie agent Otto. Olive is usually calm, brisk, and serious, unless the subject turns to her favorite basketball team, the Burly Bears. She has a morbid fear of pies. In the season 1 finale, Olive departs the series along with her partner, Otto, to run a different Odd Squad precinct as Ms. O.
- Agent Otto (Filip Geljo) - Olive's partner, and in the opening episode the newest Odd Squad agent. He turned ten in the first episode. The fun-loving Otto acts as a comic foil to Olive's straight-man demeanor, frequently annoying her. Although a rookie, Otto frequently uncovers the facts needed to solve the case at hand, even doing so in Olive's absence, proving his worth as an agent. In the season 1 finale, Otto departs the series to run another Odd Squad office as Mr. O with his partner, Olive.
- Ms. O / Agent Oprah (Millie Davis) - Head of Odd Squad, the stern Ms. O leads the organization with an iron fist. Whenever something goes wrong, she has the tendency to yell and is frequently seen sipping a juice box. Despite appearing younger than most of the agents, Ms. O's has worked for Odd Squad since the 1870s, and her actual age remains a mystery. Before she was Ms. O, she worked as an Odd Squad field agent, and became Ms. O by passing a test set up by the previous Ms. O. Her first name is Oprah.
- Agent Oscar (Sean Michael Kyer) - Odd Squad's resident scientist and gadgeteer, Oscar is a quirky genius who spends most of his time at Odd Squad Headquarters tinkering with gadgets in his lab. Incredibly knowledgeable, Olive and Otto go to him for technical solutions to their problems. Oscar has a goofy side, delivering his zany scientific rants with a generous dose of hand gestures and vocal sound effects. Oscar departed from the series in the episode "Oscar Strikes Back", where he became the president of the Odd Squad lab sector after the former president was removed from Odd Squad for misconduct.
- Math Room (voiced by T.J. McGibbon, season 1) - The virtual space construct Odd Squad agents can retreat to by twisting their badges when they need to visualize mathematical problems. They start to spin and sometimes get to the math room dizzy. The Math Room is inhabited by sentient origami papers with a unified personality. The origami can unfold to visualize numbers, charts, and instant replays as instructed by agents. The Math Room also goes by Carol, and is addressed as such by Ms. O. and O'Donahue.
- Season 2:
- Agent Otis (Isaac Kragten) - A new agent, introduced at the start of season 2, who joins to fill the opening left by the departure of Olive and Otto in the season 1 finale. He is generally very serious, and does not like to talk. There is no record of him attending the Academy, but he is the seasoned member of the new team.
- Agent Olympia (Anna Cathcart) - A new agent, introduced at the start of season 2, who joins to fill the opening left by the departure of Olive and Otto in the season 1 finale. She was given early graduation from the Academy because Ms O wanted her in the equivalent of Otto's position.
- Agent Oona (Olivia Presti): Odd Squad's resident scientist and gadgeteer. Oona took Oscar's role as the lab scientist in Odd Squad headquarters after the events of "Oscar Strikes Back".
- Polly Graph (Ava Preston) - A girl who runs a hot chocolate or lemonade stand outside her house. Odd Squad agents frequently patronize her stand. She's very fond of graphs and always has just the right visual representation to fight the situation at hand. While she is not an agent, she offers data of all sorts to agents passing by in town. Ms. O has asked her to come in to assist on cases and internal business within the squad on occasion.
- Orson (Landon and Logan Rowan) - The youngest Odd Squad agent, Orson is a baby, whose primary job is handling paperwork and answering the phone, though he also drives an ice cream truck for transportation in disguise in a few episodes.
- Agent Oren (Brendan Heard) - Agent Olaf's partner. Snarky and arrogant, Oren and his partner have an ongoing rivalry with Olive and Otto. Unlike their industrious rivals, Oren likes to weasel his way out of work whenever possible. Oren likes to brag and considers himself Odd Squad's best agent. Oren has a fear of pancakes and dreams of becoming director of Odd Squad.
- Agent Olaf (Eshaan Buadwal) - Agent Oren's partner. Olaf is happy-go-lucky and jovial in nature, but tends to be very simple-minded. He shares Oren's penchant for laziness. He loves potatoes and he dreams about becoming a dentist and fears not becoming one. It is later revealed that he is a werewolf.
- Agent Octavia (Julia Lalonde) - Agent Oz's partner. Noted in an episode, she is one of Ms. O's best agents. She is usually looking for her partner.
- Oz (Carson Reaume) - Agent Octavia's partner. On one mission, he accidentally turned himself irreversibly invisible by misfiring a gadget. He still works at Odd Squad, and is among the top agents, although it's hard for his partner to keep tabs on him.
- Orchid (Michela Luci) - One of the younger agents. She tends to be extremely stubborn. She likes to call people and things Sherman.
- Odd Todd (Joshua Kilimnik) - Agent-turned-odd and Olive's ex-partner. He was the most brilliant agent the Squad had ever seen, until he was fired off the squad, unleashed a Pienado and became Odd Todd. A recurring villain in the first season, he was outsmarted by Agent Otto and renounced oddness for other interests. In the second season, he has taken up gardening and has been seen providing assistance to agents at the squad.
- Dr. O (Peyton Kennedy) The head doctor of Odd Squad. She's know for her eccentric behavior and frequently says things that make no sense, whilst constantly reminding the agents "I'm a doctor!"
- Odell (Elijah Hammil) - A nurse agent who works under Dr. O.
- Owen (Christian Distefano) - The head of Odd Squad security.
- O'Brian (Kyle Harrison Breitkopf) - An agent engineer who runs the tube system Odd Squad agents use for transportation. Can be frequently heard calling out his catch phrase "squishinating!" as he preps the agents for tube transport. Like all the other tube system agents, his name is an Irish surname.
- Mayor Macklemore (Sean Cullen) - Mayor of the city. It is mentioned he used to be in a group called the Thirties. He once told Ms. O to do the New Years Countdown.
- Baby Genius - A mysterious infant who the Odd Squad agents bargain with for solutions to otherwise unsolvable problems. Baby Genius is never shown onscreen, only his black leather pram pushed by his Russian nanny. Baby Genius cannot speak, so his nanny, Rivka (Meghan Allen), interprets for him. The agents are terrified of him for an unspecified reason.
- The Baker (Aisha Alfa) - A recurring character in many Odd Squad episodes, the Baker runs a bakery in town and frequently requests the of Odd Squad in solving problems around her shop.
- Delivery Debbie (Ashley Botting) - A local caterer who delivers pizza. After Debbie contracts a case of "the Doubles," three duplicates of herself appear. She turns to Odd Squad for help, but later decides to keep her doubles around to help her with her pizza business
- Delivery Doug (Ali Hassan) - Debbie's chief business competition who runs a take-out egg sandwich business.
- Tommy Two-Sie (Sharjil Rasool) - A local character who likes to have two of everything. He frequently gets blamed for crimes he didn't commit and runs away from Odd Squad when confronted, even when he's innocent. He wears two hats, two shirts, two watches, and two pairs of pants held up by two belts.
- O'Hara - One of the female tube system engineers.
- O'Malley (Jack Fulton) - Another agent who works running the tube system.
- O'Callaghan (David Webster) - A tube system operator with bright red hair which looks like a wig
- O'Donnell - (Amariah Faulkner) A particularly bright and cheerful tube system engineer who wears her red hair in pigtails.
- O'Duffey - (Markus Radan) An agent engineer responsible for for the Headquarters security code.
- Oksana (Madeleine Barbeau) - Odd Squad's resident cook, who prepares all the meals by herself.
- Agent Obfusco (Jaeden Noel) - An Odd Squad agent and cross-cultural expert who speaks in obscure riddles. He's difficult for the other agents to understand, and extremely peculiar, even for an organization named Odd Squad, so the other agents try to avoid working with him. He has a sister named Obfuscolina who is even more odd and confusing for even him to understand.
- O'Donahue (Tate Yap) - Ms. O's old partner. He retired after he and Oprah failed to solve an ongoing case. After leaving Odd Squad, he worked as a fisherman, until Ms. O required his help in catching the perpetrating villain, Equal Evan. Now, he works as an undercover agent for the Squad.
- Mr. O (Bruce Salomon) - The head of the Odd Squad agency in the next town over, who has an ongoing rivalry with Ms. O.
- Agent Ori (Samuel Faraci) - New agent. He tends to run off into dangerous places.
The seal of the Odd Squad Headquarters makes use of the Droste effect. It is a Jackalope surrounded by bananas carrying a shield with the seal on it.
Season 1 (in order of U.S. release date)
- 1. Zero Effect/Bad Luck Bears (November 26, 2014)
- 2. Soundcheck/Double Trouble (November 26, 2014)
- 3. My Better Half/The Confalones (November 27, 2014)
- 4. Blob on the Job/Party Of 5,4,3,2,1 (November 28, 2014)
- 5. Reindeer Games (December 01, 2014)
- 6. Oscar and the Oscar-Bots/Picture Day (December 02, 2014)
- 7. A Case of the Sing-a-Longs/Ms. O Uh Oh (December 03, 2014)
- 8. Crime at Shapely Manor (December 04, 2014)
- 9. Skip Day/The Great Grinaldi (December 05, 2014)
- 10. The Trouble with Centigurps/Totally Odd Squad (December 08, 2014)
- 11. How to Interrogate a Unicorn/The Briefcase (December 09, 2014)
- 12. Best Seats in the House/Agent Obfusco (December 10, 2014)
- 13. Life of O'Brian/Whatever Happened to Agent Oz? (December 19, 2014)
- 14. The Jackies/Invasion of the Body Switchers (December 26, 2014)
- 15. The Odd Antidote/The One That Got Away (January 05, 2015)
- 16. Odd Outbreak/The Perfect Lunch (January 12, 2015)
- 17. Hold the Door/Flatastrophe (January 20, 2015)
- 18. Puppet Show/Mystic Egg Pizza (January 21, 2015)
- 19. 6:00 to 6:05 (January 22, 2015)
- 20. Rise of The Hydraclops/O is Not for Old (January 27, 2015)
- 21. Dance Like Nobody's Watching/Recipe For Disaster (January 28, 2015)
- 22. The Potato Ultimato/Fistful of Fruit Juice (March 31, 2015)
- 23. Soundcheck Part Deux/Jinx (April 1, 2015)
- 24. Training Day (May 25, 2015)
- 25. Trading Places/Bad Lemonade (May 26, 2015)
- 26. Robert Plant/Game Time (May 27, 2015)
- 27. The O Games (May 28, 2015)
- 28. Captain Fun/Switch Your Partner Round and Round (May 29, 2015)
- 29. Trials and Tubulations (July 15, 2015)
- 30. No Ifs, Ands, or Robots/Worst First Day Ever (July 22, 2015)
- 31. Undercover Olive (October 12, 2015)
- 32. Not So Splash/By the Book (October 13, 2015)
- 33. O vs. the Ballcano/Assistant's Creed (November 25, 2015)
- 34. Now You Don't See Me/Moustache Confidential (November 26, 2015)
- 35. The Curious Case of Pirate-itis/Oscar The Couch (January 4, 2016)
- 36. Oscar of All Trades/Swamps 'N' Gators (January 18, 2016)
- 37. There Might Be Dragons/Dawn of the Read (January 19, 2016)
- 38. Olive and Otto in Shmumberland (February 16, 2016)
- 39. Disorder in the Court (February 17, 2016)
- 40. O is Not for Over (May 30, 2016)
Season 2 (in order of U.S. release date)
- 1. First Day (June 20, 2016)
- 2. Back to the Past/Odd Squad Needs You (June 21, 2016)
- 3. Mid-Day in the Garden of Good and Odd/Failure to Lunch (June 23, 2016)
- 4. The O Team/Show Me the Money (June 27, 2016)
- 5. Flawed Squad/The Creature Whisperer (June 28, 2016)
- 6. Oscar Strikes Back (July 05, 2016)
- 7. Olympia's Day/Otis's Day (July 06, 2016)
- 8. And Then They Were Puppies/A Case of the Sillies (July 07, 2016)
- 9. Happy Halfiversary/Good Egg Bad Egg (July 08, 2016)
- 10. Night Shift/Put Me In Coach (July 11, 2016)
- 11. Extreme Cakeover/A Job Well Undone (November 7, 2016)
- 12. Three's Company/Behind Enemy Mimes (November 8, 2016)
- 13. Drop Gadget Repeat/20 Questions (November 9, 2016)
- 14. High Maintenance/Not OK Computer (November 10, 2016)
- 15. O is For Opposite/Agent Oksana's Kitchen Nightmares (March 20th, 2017)
- 16. Rookie Night/Who Let the Doug Out? (March 21st, 2017
- 17. The Cherry-On-Top-inator/Sir (March 22nd, 2017)
- 18. Orchid's Almost Half Hour Talent Show/The Perfect Score (July 17, 2017)
- 19. The Voice/Partner Problems (July 18, 2017)
- 20. Oona and the Oonabots/The Ninja Situation (July 19, 2017)
- 21. The Breakfast Club/Dr. O: Party Time, Excellent (July 20, 2017)
- 22. Haunt Squad/Safe House in the Woods (October 16, 2017)
- 23. Xs and Os/Dr. O No (October 17, 2017)
- 24. Negative Town/License to Science (October 18, 2017)
- 25. Two Agents and a Baby/Ocean and the Fly (October 19, 2017)
- 26. Hands on a Desk Chair/There's No "O" in O-Bot (March 26, 2018)
- 27. Shapely University/Slow Day (March 27, 2018)
- 28. Villains In Need Are Villains Indeed/Happily Ever Odd (March 28, 2018)
- 29. Where There's a Wolf, There's a Way/New Jacket Required (June 11, 2018)
- 30. The Deposit Slip-Up/Villains Always Win (June 18, 2018)
- 31. Other Olympia/Total Zeroes (June 25, 2018)
- 32. It Takes Goo to Make a Feud Go Right/Friends of Odd Squad (October 5, 2018)
- 33. Saving Agent Orson/The Scientist (October 22, 2018)
- 34. Who Is Agent Otis? (January 21, 2019)
- 35. Odds and Ends (January 21, 2019)
Television Series (in order of release date)
- The Heising Simons Foundation. Unlocking Knowledge, Opportunity, and Possibilities. (Early Season 2 episodes)
- A Cooperative Agreement from the U.S. Department of Education (Season 1)
- The Corporation for Public Broadcasting's Ready to Learn Grant (Season 1 and early Season 2 episodes)
- Viewers Like You/Thank You