Purpose: Aromatherapy (AT) is a complementary therapy recently used in the perianesthetic period. However, the scientific data on its effectiveness are limited. The aim of this systematic review is to present and analyze the results of all randomized controlled trials (RCTs) that studied the effectiveness of AT as a complementary treatment for postoperative pain. Design: PubMed and Cochrane Library databases were searched from 1965 to December 2015. Nine randomized controlled trials that met the inclusion criteria were eventually included. Methods: The studies included a total of 644 patients, who underwent various types of surgeries. The modified Jadad scale with eight items was used for the methodological evaluation of the RCTs. Findings: Five RCTs support AT, which can alleviate postoperative pain, whereas four found no statistically significant differences between groups. Conclusions: Although AT is presented as an inexpensive complementary treatment with a low rate of adverse effects that improves patient satisfaction, it cannot be determined that there is sufficient evidence to conclude its effectiveness as a nonpharmacologic approach to the reduction of postoperative pain intensity.