Today, the production of extremely low-frequency electromagnetic fields (ELF-EMFs) has significantly increased. This study aimed to investigate the effect of the ELF-EMFs on the structure and function of the brain in male rhesus monkeys in terms of visual learning (VL), visual memory (VM), and visual working memory (VWM). To conduct the study, four monkeys were selected, of whom two monkeys were irradiated by 12-Hz ELF-EMFs with a magnitude of 0.7 microtesla, and two monkeys were tested without irradiation (control group). A blood sample was taken in three stages, namely pre- and post-irradiated and the recovery phases. Changes in the plasma levels of sodium, potassium, and adrenocorticotropic hormone (ACTH) were evaluated. Moreover, gene expression of N-methyl-D-aspartate (NMDA) receptors was assessed. The anatomical change of the brain's prefrontal area was measured by magnetic resonance imaging and Digital Imaging and Communications in Medicine LiteBox file. The abilities of VL, VM, and VWM significantly improved after the irradiation. Furthermore, the expression of the NMDA receptors gene and the plasma levels of sodium, potassium, and ACTH significantly enhanced after the irradiation. However, the prefrontal area was not significantly affected by the irradiation. No significant differences were observed in any of the studied factors in the control group. Our findings suggested that ELF-EMFs irradiation at 12 Hz positively affected VL and VWM. Consequently, 12-Hz ELF-EMFs irradiations can be widely applied to improve cognitive abilities in monkeys.