The opening of the preorbital gland in deer serves as a visual communication and has been linked to a wide variety of behavioural situations. As we reported recently, all previous long-term studies on preorbital gland opening were carried out on only one species, whereas case reports on six other rarely studied species have shown associations with different behaviours, thus greatly increasing our overall understanding of the real function of this gland in animal visual communication. Here, we report for the first time preorbital gland opening in the barasingha (Rucervus duvaucelii) in social contexts as observed in a wild population in Kanha National Park, India. We observed this behaviour in two different contexts: agonistic and sexual. Moreover, our record of preorbital gland opening during copulation is the first one amongst cervids. Our findings of preorbital gland opening in both contexts in wild barasingha indicate that the gland was opened only when the individual was highly excited. We suggest that preorbital gland opening may be an important behavioural indicator of an individual involved in a serious intraspecific interaction, and thus a useful tool with which to distinguish between playful and serious behaviours, especially in agonistic and sexual situations.