The safety of human exposure to an ever increasing number and diversity of electromagnetic field (EMF) sources both at work and at home has clearly become a public health issue. To date many in vivo and in vitro studies revealed that EMF exposure can alter cellular metabolism, endocrine function, immune activity, reproductive function, and fetal development in animal system. The major parameters found to be altered in cells or individuals following EMF exposure include an increase of free radicals, DNA damage, cancer risk, developmental defect, and reproductive dysfunctions. Epidemiological studies reported EMF can increase life threatening illnesses such as leukemia, brain cancer, amyotrophic lateral sclerosis, clinical depression, suicide, and Alzheimer`s disease has been identified. These effects of EMF exposure differ according to duration of exposure, frequency of waves, and strength (energy) of EMF. In the present review, we briefly introduced the physical properties of EMF and summarized the effect of EMF on human and wildlife animals according to types of EMF, duration of exposure at cellular and organism levels.