In captivity, its temprament is much the same. Mountain pygmy possums have been seen running over the backs of each other with little disturbance. They also seem to socially groom each other. The behavior of B. parvus has a characteristic pattern, with the male first pursuing a female and sniffing her anal region. If the female chooses to mate, she allows him to mount and clasp her flanks.
Copulation lasts several minutes, after which the male leaves.
After birth and growth of young males, females are aggressive towards them and force them to leave the natal area. Older males leave first, followed by juvenile males and sometimes juvenile females. Female's natal areas have communal nesting sites and overlapping home ranges. Older females tend to share their ranges with up to 10 younger females. It is likely that the younger females are genetic descendants of the older female.