Externally, Betazoids are physically indistinguishable from Humans in every aspect but one: the irises of their eyes are completely black. They can even cross-breed with Humans, along with other humanoid races like Klingons and Tavnians.

Betazoids are natural telepaths. Most develop their telepathic skill in adolescence, but a few are born with their telepathic abilities already active. These individuals are almost always extremely talented and powerful in telepathic terms, but also unable to screen out the noise of other people's minds, so they generally suffer mental problems of varying severity depending mostly on when the problem was diagnosed. On the other end of the scale are a few individuals who develop psionic abilities which are far below average for this species. Those Betazoids are barely able to sense even strong emotions of other people, not to speak of thoughts.

The common psionic abilities of Betazoids are going from sensing thoughts and/or emotions, over projecting thoughts and/or emotions, to manipulating the minds of others. How capable they are in performing any of those feats depends somewhat on their genetically defined psionic strength, their psionic training, their familiarity with the scanned being, their general mental and physical condition and the species of the subject race. Betazoids have been able to read the emotions/thoughts of non-corporeal beings such as Nagilum in the episode 'Where Silence Has Lease' or the energy vortex creature in the episode 'Time Squared' or gauge the mental prowess of beings such as Q. Other times they have been totally unable to read corporeal creature's minds, such as Ferengi and Changelings. Data theorizes that the reason they may not be able to read Ferengi is the structure of their brains. And he himself was able to be read by Deanna Troi when his brother Lore used the emotion chip to transfer bad emotions to him. At one point, when Deanna Troi lost her empathy temporarily she commented that Will Riker was like a holodeck character to her, completely devoid of emotion, as if she had never experienced a lack of empathy from any sentient before. The traveler was also not able to be read by Deanna Troi as well.

Inter-species reproduction involving Betazoids often affects the psionic abilities of the offspring - most commonly the children of such a union develop empathic abilities as their primary psionic talent, while their telepathic abilities, though existing, are rather below average for Betazoids. Usually the telepathy of these half-breeds, without extensive training, is limited to communication with other empaths or telepaths and full telepathic contact with emotionally very close persons (for example, an imzadi). All full Betazoids are unable to read the thoughts of Ferengi, Breen, Ullians, or Dopterians, but some half-Betazoids have been occasionally successful in sensing the emotions of some of these species. Additionally, even full Betazoids seem to be able to psionically influence some of these species. According to the novel The Battle of Betazed, some hidden mental teachings are able to unlock the ability of telekinesis in Betazoids.

Due to their telepathy, Betazoid culture embraces honesty almost to a point considered rude by other cultures. Lwaxana Troi, on numerous occasions, commented on her befuddlement at the Human practice of fibbing to spare others' feelings or for politeness' sake.

Betazed has a complex hereditary nobility; prominent Betazoid diplomat Lwaxana Troi, for example, is "Daughter of the Fifth House, Holder of the Sacred Chalice of Rixx, and Heir to the Holy Rings of Betazed." Betazoid tradition has children genetically bonded to a future spouse.

In the Betazoid wedding ceremony, all participants are traditionally naked, not only the bride and groom, but the guests as well.

At one time, it was fashionable for Betazoid women to wear elaborate wigs that encaged small animals. The practice, which was cruel to the animals, was stopped when one (unknown) woman stood up against it.