Taenia pisiformis is one of several parasitic tapeworms that infect dogs and other canines, which are the definitive host (or primary host), with rabbits most often serving as the intermediate host. The tapeworm has a simple anatomy, which is dedicated almost entirely to reproduction.

The adult has a head (scolex) with suckers or hooks that are used to attach to the host. Tapeworms have a very simple nervous system and, lacking a digestive tract, absorb nutrients directly through an external layer of cuticle. Most species are hermaphroditic (containing both sexes) and can reproduce independently. During its lifetime, each tapeworm can produce hundreds of reproductive segments called proglottids, each of which can contain up to 40,000 larvae.

The proglottids pass through the digestive tract of the primary host and are eliminated with feces. Intermediate hosts (generally prey animals) ingest the larval forms when grazing on contaminated grass. Once ingested, the larvae emerge in the digestive tract where they burrow through the intestinal wall into a blood vessel and are carried to muscle tissue or some other organ tissue (various species of tapeworms select different tissues as destinations for the larvae). The period during which the larvae are encysted in the tissue of the intermediate host is known as the cysticercus, or bladder worm, stage.

When the infected muscle or organ of the intermediate host is eaten raw by a dog or other canine, the cysticerci emerge and travel to the animal's intestine where they will attach and grow into adult form. Tapeworms can also reproduce by shedding living segments that grow into another tapeworm when ingested by another primary host.