Introduction The risk of contralateral lymph node metastases following unilateral sentinel lymph node (SLN) metastases in patients with vulvar cancer(s) remains to be systematically assessed. Material and methods We performed a multicenter, retrospective registry-based study of 476 patients with vulvar cancer. The primary outcome measure was the rate of contralateral non-SLN metastases in the case of positive unilateral SLN. Results Out of 476 patients with primary vulvar cancer, 202 received SLN biopsy: 58 unilateral and 144 bilateral. Out of 66 patients with unilateral metastatic SLN, 62 (93.9%) received contralateral lymphadenectomy-18 after unilateral and 44 after bilateral SLN biopsy. In the study group, 132 SLN were assessed with a median number of 2 (range 1-4) per patient and 76 of these were positive. Lymph node-positivity was associated with advanced tumor stage, as well as lymph and vascular space invasion. In the group of patients with bilateral inguino-femoral lymphadenectomy, 1004 lymph nodes were resected with a median number of 15 (range 10-29) per patient. After full dissection of the inguino-femoral lymph nodes, no contralateral non-SLN metastases were found. Conclusions The risk of contralateral non-SLN metastases in patients with unilateral SLN metastases was low. Therefore, the impact of contralateral lymphadenectomy on patient survival should be investigated in further studies.