Primary retroperitoneal serous cyst adenomas (PRSCs) are extremely rare thin-walled cystic lesions whose pathogenesis is not well understood. Clinical presentation varies depending on the lesion's size and location, i.e., larger lesions compress adjacent organs, giving the impression of malignancy. Although advances in imaging techniques enable to identify various characteristics of retroperitoneal cystic lesions, there are no pathognomonic signs to confirm the diagnosis. The exact diagnosis is based on the histology after complete surgical excision. An open surgical approach is considered the traditional method of complete resection; however, laparoscopic techniques have increasingly been employed. Diagnostic aspiration is discouraged due to the potential risk of seeding if the lesion is malignant. We present the case of a 51-year-old woman who underwent complete excision of a large right retroperitoneal cyst, histologically confirmed as PRSC with a review of the background and management options of this phenomenon.