Background: Lymphatic filariasis is caused by a mosquito-borne parasite affecting roughly 100 million people round the world. There is consensus that hydrocele is the most frequent clinical manifestation of bancroftian filariasis. In endemic areas, about 40% of men are suffering from testicular hydrocele. With this background, the present study was aimed to find the incidence of filariasis in clinically diagnosed primary vaginal hydrocele.Methods: A hospital based prospective, cross-sectional study was conducted with 60 patients diagnosed clinically as primary vaginal hydrocele coming to the department of surgery, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pimpri, Pune, to assess the incidence of filariasis.Results: Anti-filarial antibody and circulating filarial antigen in serum were detected in 5 (8.3%). Out of 60 patients and anti-filarial antibody was detected in hydrocele fluid of 2 (3.3%) patients. 2 patients out of these 5 showed microfilaria in peripheral blood smear and eosinophilic infiltrates in histopathological examination of sac.Conclusions: In 5 out of 60 cases both anti-filarial antibody and circulating filarial antigen in serum are positive thus proving that incidence of filarial hydrocele is 8% in clinically diagnosed primary vaginal hydrocele which is supposed to be idiopathic. Even though these cases have presented as clinically primary vaginal hydrocele, they are found to be filarial hydrocele after analysis of serum and hydrocele fluid. So, it is advised that all cases of clinically diagnosed primary vaginal hydroceles should be investigated for filariasis and if not, may lead to recurrence in these cases.