Basilisk venom was extremely powerful and could kill a person within a little more than a minute at best, making the person drowsy and blurry-visioned before they died. This powerful venom was one of the few substances known to be capable of destroying Horcruxes, causing them fatal damage that could not be repaired. It only had one known antidote: phoenix tears, which happened to be very rare, decreasing the venom's deadliness.

The venom's potency was extremely long-lasting, as Hermione Granger was able to use the venom from the fang of a Basilisk that was dead for nearly five years.

Basilisk venom was one of the few poisons that were not curable by bezoars.

In 1993, Harry Potter stabbed the roof of the Basilisk's mouth with the Sword of Gryffindor and ended up getting a fang splintered into his arm. Tom Riddle described the venom as being able to kill Harry in a little more than a minute, though Fawkes's tears healed Harry's arm and cleansed the poison.