Nano Zero Valent Iron (NZVI) is emerging as new selection for the treatment of contaminated soil and groundwater. Due to their small size, the nanoscale particles are more reactive than granular iron which is conventionally applied in reactive barriers and can be applied for in situ treatment. NZVI effectively reduces a large number of organic and inorganic compounds, including halogenated hydrocarbons, organic dyes, antibiotics, heavy metal ions, etc. Its inner core (iron(0)) has exerts a reducing character towards pollutants, whereas the iron oxide (FeO) outer shell acts as a reaction site for chemisorption and the adsorption of contaminants via electrostatic interactions. Generally, NZVI can be produced using physical or chemical methods either by reducing the size of bulk iron to nanoscale (top-down approach) or building up nano iron from atoms generated from ions or molecules (bottom-up approach). Some of These methods include liquid phase-reduction, milling, carbothermal reduction, ultrasound assisted method, electrochemical and green synthesis.