Siphonophores feed on crustaceans (shellfish), tiny fish, and other small animals. They capture their prey by trailing long tentacles. The tentacles contain stinging capsules called nematocysts. The nematocysts harpoon prey and inject a toxin, immobilizing it. Many siphonophores simply wait for prey to swim into their tentacles. At least one deep sea species has been found to lure its prey with light.

Siphonophores reproduce sexually through the use of specialized zooids. In some species, the entire colony functions as either male or female. Colonies of other species have both male and female parts. A new siphonophore begins with a single zooid formed from a fertilized egg. This zooid produces the rest of the colony through budding. Budding is a form of asexual reproduction in which a new organism grows from a bud on the original organism.