The mating system of these lemurs has not been reported. However, other species in the genus Eulemur are either monogamous or polygynous. It is likely that E. fulvus is similar. Unlike other members of the genus, females are not usually dominant to males, so the degree to which females exert active mate choice is not known. (Nowak, 1999)
Brown lemurs reach sexual maturity between 1 and 2 years of age. Their mating habits are very seasonal with mating occuring sometimes in late May (Sanford's lemurs only) but usually throughout June and July (all subspecies). The gestation period for these animals is approximately 120 days. Infants are born in the fall, between September and November. Only one infant is born per year to each mother.
For the first three weeks of their lives, young lemurs hang onto the mother's bellies. They alter their grasp only to nurse. After three weeks have passed, they shift and ride on the mother's backs. They then begin to take their first steps. Following this, they start to sample solid food, nibbling on whatever the other members of the group happen to be eating. This is their first sign of independence. Nursing continues but its importance in the infant's diet tapers. The young lemur is weaned after approximately 4 to 6 months - usually by January.
The role of males in parental care in this species has not been described.