Biosynthesis of nanocomposites by plant, fungi and bacteria is considered as one of the promising ecofriendly approach alternative to chemical and physical methods. Nowadays, the application of the biosynthetic nanocomposites in the removal of different recalcitrant dyes has attracted more consideration. Different fungal isolates were examined for their capability for magnetite nanoparticles synthesis. The exo-metabolite of Aspergillus tamari was found to be the most suitable for the Fe₃O₄-nps biosynthetic process. The produced nanocomposite was characterized using various devices. Transmission electron microscope (TEM) showed spherical nanoparticles with 9 nm size. SEM micrograph shows an aggregation of spherical nanoparticles. In the batch adsorption process, the removal efficiency of methyl orange (MO) dye was 84.9% within 20 min of incubation period. The adsorbent dosage of 2 g/l displayed the maximum MO removal rate at initial dye concentration of 80 mg/l. The MO removal rate was sharply improved as a response for pH variation, while exhibiting the maximum rate at pH of 5.0. Therefore, the Fe₃O₄-nps synthesized by harnessing the exometabolites of A.tamarii can be considered as a promising adsorbent material for removal of toxic/recalcitrant dyes from wastewater.