Today, nanotechnology is growing due to its wide and abundant application in science and industry. Although there are chemical and physical methods for nanoparticle synthesis, it is necessary to use synthesis methods without the use of toxic chemicals and byproducts. In this regard, the use of plant extracts is hopeful because plant extracts contain many compounds that could reduce metal ions to nanoparticles (NPs). Glycyrrhiza glabra is one of the important medicinal plants, which is a rich source of secondary metabolites that can synthesize, stabilize and coat NPs. In this study, the aqueous extract of Glycyrrhiza glabra (Licorice) was used to synthesize nickel nanoparticles (NiNPs) and this green synthesis was affordable, cheap and easy. Morphology and physicochemical properties of particles were investigated. Our results showed that green synthesized NiNPs were amorphous and apparently rod-shaped with a hydrodynamic diameter size of 335 nm. The zeta potential of the particles was -28mV. Therefore, these particles can be suitable candidates for interacting with positively charged compounds. This study has proved a green, safe, and biodegradable NiNPs synthesis method, which can be used in many fields such as biology, medicine, and agriculture for many usages, gene delivery, and biomolecules purification.