The aim of this study was to investigate the effects of mobile phone electromagnetic radiation (MP-EMR) on the thyroid glands and hormones in Rattus norvegicus brain in term of thyroid function, reactive oxygen species (ROS), and monocarboxylate transporter 8 (MCT8) concentration. Forty rats were divided into different groups: control (without EMR exposure), EMR1 (120-min/day exposure), EMR2 (150-min), and EMR3 (180-min). The levels of serum thyroid stimulating hormone (TSH), thyroxine (T4), and malondialdehyde (MDA) and brain and MCT8 were measured using enzyme-linked immunosorbent assay. One-way analysis of variance followed by the Duncan test was used to analyze the data. Our data indicated that the levels of serum TSH and T4 in all the EMR groups were lower significant postexposure compared to the control with P < 0.01 (EMR1 and EMR2) and P < 0.001 (EMR3), suggesting hypothyroidism due to MP-EMR exposure. Increased MDA and decreased MCT8 levels were also observed following the intervention; however, the changes in both concentrations were notably significant after being subjected to 150-min and 180-min of exposure. In conclusion, a significant reduction in TSH, T4, and MCT8 levels indicated thyroid dysfunction due to MP-EMR exposure.