Infrared thermography is an increasingly used technology in veterinary science and in mammal physiology. However, its employment as a quantitative method to accurately determine mammal surface temperatures requires knowledge of the emissivity of that individual’s pelage. To-date, few researchers have measured emissivity of their study animal’s pelage, or determined the relationship between fur metrics and emissivity. Instead, studies have relied on historic values generated from a single study on arctic fauna. Therefore, this study aimed to determine pelage emissivity for a range of mammal species and to establish the putative correlation between emissivity and fur metrics. Emissivity was measured at different sites of the body for 22 species. In addition, hair length and hair diameter were measured from hairs collected at the same sites that emissivity was measured. The mean pelage emissivity of sampled specimens was 0.86 ± 0.01, which was lower than the range (0.95–1.00) reported previously. Emissivity was neither related to taxonomy nor to hair metrics but may be related to other factors not measured in this study. Contrary to common practice, a single (0.98) or a narrow range (0.95–1.00) of emissivity values is unlikely to be appropriate for obtaining accurate surface temperature readings in quantitative IRT studies on mammals.