In the wild, they are found in groups of 2-8, often made up of family members. The groups comprise breeding pair, offspring of 1 or 2 litters and possibly other relatives. The groups are usually nuclear families, but can be extended families. These tamarins are territorial and defend their area with scent markings and vocalized threats. Some signs of aggression are an open mouth, an arched back and staring.
Golden lion tamarins groom themselves much like other primates.
Mainly the males groom the females. Adults spend a lot of time grooming and huddling. The juveniles play a lot. They chase each other around and wrestle. They have a quad-gait, meaning they use all fours to get around.