Like other vipers, the Gaboon viper has a thick body, keeled scales and triangular head. With hinged fangs at length of up to 5cm at the front of the mouth, these vipers have the longest fangs of any venomous snake. Weighing more than 20 kg and growing to lengths of more than 1.8 m, Gaboon vipers are also the largest vipers in Africa. The biggest individuals have heads that measure nearly 15 cm across at their widest point. Their symmetrical and striking pattern helps them blend seamlessly into the leaf litter on the forest floor. Its broad, whitish-cream head imitates a fallen leaf perfectly, right down to the dark central vein.

Passive hunters, these snakes lie in wait for whatever small creatures that come within striking range. Most snakes strike and release, but this viper holds on till its prey breathes its last. That said, this species is known for its placid nature. If it senses a threat, it will raise the upper part of its body and hiss — it usually hesitates to bite. Only in rare cases where the snake was stepped on before it could get out of the way, or when movements had been mistaken as those of prey, have humans been bitten. Whether a strike results in mere pain or rapid death depends on whether the snake injects venom into its bite, and how much.

Males of this species engage in combat during the breeding season. The first male ‘picks’ a fight by rubbing his chin along the back of another. In response, the second male rears its head up high. The first male follows suit and their necks intertwine. Levelling their heads, they face off and push, bodies locking together as they switch positions. Oblivious to everything but their rivalry, they remain locked in combat even after falling off a surface or into water. When they tire, they may take a consensual break before resuming. The victor that succeeds in pushing the other's head to the ground gains mating rights to the female.