Brave Captain Barnacles is a polar bear extraordinaire and leader of Octonauts crew. He is always the first to rush in and help when there is trouble. Besides adventuring, Barnacles also enjoys playing his accordion and writing in his captain's log.

Kwazii is a daredevil orange kitten from the mysterious far east. She loves excitment and travelling to exotic places. Her favourite past times are long baths, swordfighting and general swashbuckling.

Peso is the medic for the team, he enjoys putting bandages on cuts and tending to wounds. He's not too fond of scary things, but fortunately his big heart usually wins over all monsters.

Shellington is a nerdy sea otter scientist who loves doing field research and lab work. Unfortunately, he is easily distracted by rare plants and animals, which sometimes places him in dangerous situations that the other Octonauts have to get him out of.

Sauci is the sweet sausage dog who oversees operations in the Octopod control room and launch bay. She manages all ship traffic and ensures all the computers are in good working order.

Tweak is the mechanical engineer for the Octopod. She keeps everything working properly below deck in the engine room and maintains all Octonaut vehicles, GUP-A to GUP-E. Tweak loves all kinds of machinery and enjoys building strange contraptions that sometimes work in unexpected ways.

Professor Inkling is a brilliant dumbo octopus oceanographer. He is the original founder of the Octonauts with the intention of furthering underwater research and preservation. Because of the Professor's small size and delicate big brain, he prefers to stay at the Octopod and contact the team through their special communicator.

Tunip is one of many vegimals, a special breed of underwater critter (part animal / part vegetable) who like to help out around the Octopod. Vegimals love to cook barnacle dishes: barnacle pasta, barnacle cakes, barnacle cookies, barnacle sandwiches...