Nitro aromatic compounds such as, 2-nitrophenol and 4-nitrophenol are identified lethal to human due to their constructive role in causing the problems such as, vertigo, headache, fainting and mental disturbance. A strong remedy is desired to treat aqueous environment for these toxic aromatic species. In this pursuance, gum arabic (GA) microgels were synthesized to entrap the metal nanoparticles (NPs) for catalytic reduction of 4-nitrophenol (4-NP) to it reduced counterpart, 4-aminophenol (4-AP). A reverse micellization method was adopted to prepare GA based spherical microgels with a high yield of up to 79% in 5-50 μm size range via successful crosslinking by divinyl sulfone (DVS) in gasoline medium. These GA microgel based matrices were then used to fabricate nickel (Ni) and copper (Cu) NPs based nanocatalysts and were designated as GA-Ni and GA-Cu, respectively. The successful synthesis of the microgels and afterwards in situ fabrication of NPs in them was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Moreover, the catalytic reduction properties of GA-Ni and GA-Cu microgels toward 4-NP were investigated. Interestingly, 0.05 g feed of each GA-Ni and GA-Cu microgels reduce 4-NP to 4-AP in less than 10 min of total mixing time at room temperature. This catalytic approach follows pseudo-first order rate kinetics and the rate constant (Kapp) values calculated for GA-Ni and GA-Cu based catalysis were 0.127 min-1 and 0.66 min-1, respectively. © 2019 Elsevier Ltd.