Endometriosis is defined as a disorder in which the glands and stroma of the endometrium grow and shed periodically outside the uterine cavity. Highly prevalent in women of reproductive age, the most common clinical manifestations are chronic pelvic pain and infertility. The pathogenesis of endometriosis may be multifactorial, including factors of anatomy, immunity, inflammation, hormones (estrogen), oxidative stress, genetics, epigenetics, and environment. There are generally three types of endometriotic disease, namely peritoneal, ovarian, and deep infiltration. For the same patient, there may be a single or multiple types concurrently. The different manifestations of these types suggests that they each have their own etiology. Numerous studies have shown that the evasion of endometrial cells from peritoneal immune surveillance helps establish and maintain peritoneal endometriosis, but the specific mechanism is not well understood. Likewise, the molecular mechanisms of endometriosis-related infertility have not been clearly elucidated. This review attempts to identify the role of peritoneal immunity in peritoneal endometriosis and related infertility, especially in the aspects of molecular mechanisms.