Strangles caused by the bacterium Streptococcus equi, the signs of equine strangles include fever, nasal discharge and depression, and abcesses can also develop around the head and neck. This study was conducted to evaluate serum values of these elements in horses with strangles and compare with safe animals. Horses were recognized based on clinical and laboratory findings (culturing of the nasal and lymph node discharges). After taking history and recording it, blood samples from jugular vein was obtained and sera were separated. In that time, we also sampled from healthy animals with the same situation. Serum values of cobalt, iron and phosphorous was measured by spectrophotometry and biochemical available kits, respectively. The mean value of iron in the horses with strangles was 104.11±2.21 μg/dl and in control group was 113.10±1.91 μg/dl, so, there was significant difference among groups (P=0.004). The mean value phosphorous in ill animals insignificantly was lesser than control group (P=0.113). Its value was 4.21±0.16 and 4.61±0.19 mg/dl, respectively. The mean value of cobalt in the horses with strangles was 1.36±0.15 μg/dl and in control group was 1.75±0.14 μg/dl, so, there was significant difference among groups (P=0.062). Finally, in horses with strangles, the decrease in serum values of iron, cobalt and copper showed is not significant. So, considering the role of these elements in hematopoiesis and immune system, the administration of supplements containing these elements (oral or injection) is suggested.