BACKGROUND: Fire extinguishing operations are carried out by firefighters equipped with personal protective equipment (PPE) in dangerous environments. Although PPE protects firefighters, it can affect many physiological parameters. OBJECTIVE: This study aimed to investigate the effects of PPE on firefighters’ heart rate (HR), oxygen consumption (OC) and body temperature (BT). METHODS: This systematic review thoroughly reviewed relevant articles in the reliable databases “Web of Science”, “Embase”, “IranDoc”, “IranMedex”, “SID”, “Magiran”, “Google Scholar”, “PubMed” and “Scopus” from 2010 to 2021. Some of the used search terms were “firefighters”, “personal protective equipment”, “heart rate” and “oxygen consumption”. RESULTS: Out of the 405 studies identified through the systematic search, 18 articles were eligible according to the Joanna Briggs Institute (JBI) checklist, among which 11 studies were conducted in North America, three in Asia, two in Europe, and two studies in Oceania. According to the review of studies, PPE increased HR, BT, and OC. The type of PPE components, the weight of the equipment, the kind of activity of firefighters, and weather conditions were among the influencing parameters on the extent of PPE’s influence on these physiological parameters. CONCLUSION: The results of the studies show that PPE separately and collectively affects the physiological parameters of HR, BT and OC. To reduce these effects, it is necessary to pay attention to several items, including the weight of PPE, the type of PPE ingredients in different weather conditions, and the type of activities of firefighters in PPE design.