The Quarren were a squid-like species with four facial tentacles which protruded from their lower jaw. Their skin-color range included various hues of orange, salmon, tan, pink, and purple. They had a pair of deep turquoise eyes, finned hands with suction-tipped fingers, and small tusks on their mouth. In the two long protrusions that extended from either side of their faces, Quarren had gill-like structures that were actually hearing organs.

An amphibious species native to the aquatic world of Mon Cala, the Quarren were natural swimmers and were most comfortable underwater, prefering to be immersed in liquid. They were also bipedal beings that could walk and sit upright. Capable of spitting clouds of black ink as a defensive measure in combat, such ink could also be released from a Quarren’s body when cut open at the mid-section by a lightsaber, a mortal act. Quarrens would also release ink in their sleep during nightmares. Any atmosphere without humidity could be bad for a Quarren’s skin and nasal passages, resulting in off-world Quarren turning to products like moruga nut oil and taking extremely hot showers.

The Quarren species had male and female sexes, and their form resembled that of humans. The Quarren Jethpur spoke Quarrenese, though the species was able to speak fluent Galactic Basic Standard.

Similar to their neighboring sentient species—the Mon Calamari—who shared their homeworld, the Quarren typically wore clothing that covered most of their body, though left their heads unadorned. However, the Quarren pirate Kragan Gorr wore an Imperial officer battle armor helmet.

The Quarren and Mon Calamari also shared the capability of sustaining cybernetic modifications. A hybrid between the two existed during or prior to 146 BBY.