Both male and female red-flanked duikers mature at about nine months of age. The female comes into oestrus once a year and the gestation period is about eight months, with a single offspring being born in the dry season or near the start of the wet season. The newly-born juvenile weighs about and quickly makes its way into concealing vegetation, only coming out when its mother returns to nurse it. Immediately after birth and when grooming its infant, the mother marks it with the secretions from her preorbital glands. It is weaned when it weighs about and there is no further parental involvement.