Endometriosis is a common gynecologic condition affecting as many as 1 per 10 women. Transvaginal ultrasound (TVUS) has become a frontline tool in the diagnosis of deep infiltrating endometriosis (DIE) before surgery. The primary aim of this review was to determine the accuracy of TVUS for DIE. The secondary aim was to determine accuracy specifically when a sonographer performed the TVUS examination. A systematic review was performed, searching literature by following a population, intervention, comparator, and outcome outline. MEDLINE, Embase, Emcare, and Google Scholar were searched in July 2018 and in November 2019. Including "sonographer" in the search terms yielded no results, so our terms were expanded. Two hundred and four articles were returned from the searches, and 35 were ultimately included in the final review. Analysis of the returned articles revealed the TVUS is a valuable diagnostic tool for DIE before surgery. Sensitivities ranged from 78.5% to 85.3%, specificities from 46.1% to 92.5%, and accuracies from 75.7% to 97%. Most authors reported site-specific sensitivities and specificities, which varied greatly between locations. Site-specific sensitivities ranged from 10% to 88.9% (uterosacral ligaments), 20% to 100% (bladder), 33.3% to 98.1% (rectosigmoid colon), and 31% to 98.7% (pouch of Douglas). Site-specific specificities ranged from 75% to 99.6% (uterosacral ligaments), 96.4% to 100% (bladder), 86% to 100% (rectosigmoid colon), and 90% to 100% (pouch of Douglas). Transvaginal ultrasound is an accurate tool in the diagnosis of DIE; however, limited data exist as to whether this technique is accurate when performed by sonographers. More evidence surrounding the reliability between operators is also needed.