Hellbenders are aquatic organisms throughout their life and remain active year-round. Hellbenders become active after dark, leaving shelter to forage, feeding primarily on crayfish, fish, frogs and a variety of invertebrates. Courtship and breeding begin in late summer. Sexually mature salamanders migrate to and congregate within certain areas to breed. Hellbenders are more conspicuous at this time of the year and some diurnal activity may be observed on overcast days.
Males excavate a large nest chamber beneath a rock in preparation for breeding.
Gravid females are either attracted to or corralled into the nest sites by the males. Egg laying is initiated about the first week in September. Females simultaneously deposit two long strings of eggs in a softball-sized yellowish mass onto the nest bed. Eggs are fertilized externally as they are being deposited. The breeding pair slowly sways within the nest cavity during fertilization, thereby ensuring a thorough mixing of seminal fluid and eggs.