Background Treatment of a sunken appearance of the temporal region using injectable fillers is a popular procedure. The temporal fossa has very complex anatomy due to multiple vessels running in the different tissue layers. A severe complication in the form of non-thrombotic pulmonary embolism (NTPE) can occur as a result of an inadvertent injection in the middle temporal vein (MTV) while performing temporal fossa filler procedures. Therefore, in-depth knowledge and understanding of the MTV anatomy are essential for successful and safer injectable procedures of the temporal fossa. Objectives While there have been many studies to describe the arteries in this region, there is limited information about the location and course of the middle temporal vein. This literature review is aimed at providing detailed information about the course, depth, and size of the MTV to help aesthetic practitioners in performing safer temporal fossa filler injections. This information is imperative to delineate the ‘venous danger zone’ in the temple region. Methods The preferred reporting items for systematic reviews and meta-analyses guidelines were used for this review. A literature search was performed to find the articles providing details about the MTV anatomy and the measurements related to its course and size. Results A review of the literature showed that the MTV displays a consistent course and depth in the temporal region, with high variability in its diameter. The middle temporal vein width varied between 0.5 and 9.1 mm in various studies. The middle temporal vein receives many subfascial tributaries from the surface of the temporalis muscle, and for most of its course runs in the fat pad enclosed between superficial and deep layers of the deep temporal fascia. A ‘venous danger zone,’ in the interfascial planes of the temporal fossa, which contain the main part of the MTV and its tributaries, has been proposed in this paper. Conclusions The temporal fossa filler procedures need great caution, and knowledge of the depth and course of the MTV is essential for avoiding NTPE. Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .