Several small specimens have been reported as architeuthids, but close inspection reveals them to belong to other families. Cephalopods are known to be very fast growing animals. But the age at maturity of Architeuthis is not known with certainty. Even at the rapid growth rate expected in cephalopods, the attainment of a mass of 500 kg or more in fewer than 3 years is impressive. As in most oegopsids, females have a single median ovary in the posterior end of the mantle cavity, paired, convoluted oviducts along which mature eggs pass, then exit through the oviducal glands, and large nidamental glands that produce quantities of gelatinous material.
Males tend to reach sexual maturity at a smaller size than do females.
As in most other cephalopods, the single, posterior testis produces sperm that move into a complex system of glands that manufacture the spermatophores. These are stored in an elongate sac, Needham's sac, from which they are expelled during mating. The Needham's sac of fully mature males is packed with hundreds of spermatophores. Needham's sac terminates in the penis. The penis is so elongate that it extends anteriorly beyond the mantle opening.