Despite nanotechnology got a high public awareness due to its implementation in various human activities, the effect of nanoparticles on bacterial performance in wastewater treatment is still unclear. This study examines the role of magnetite nanoparticles (Fe3O4 NPs) on the dairy effluent nitrate and phosphate bioremediation using diverse inoculum sources. Two inoculum sources (wastewater and sludge) were got from the dairy wastewater treatment plant unit. A culture was prepared to check the role and efficacy of Fe3O4 NPs. After five days of incubation, the culture of dairy diverse inoculum sources was verified to be effective in effluent treatment. By applying sludge as an inoculum source, the reduction efficacy was enhanced up to 48.54% and 46.13% for nitrate and phosphate, respectively compared to control. In the case of applying wastewater as an inoculum source, the reduction was enhanced up to 64.12% and 36.85% for nitrate and phosphate, respectively compared to control. Furthermore, the bacterial abundance showed a significant variance between control and another sample (high abundance than control). Results revealed that Fe3O4 NPs can improve the microbial growth of diverse inoculum sources which are efficient in the bioremediation of dairy effluent. Overall, the concentration (40 ppm) of Fe3O4 NPs was obtained the optimal abundance for inoculum sources and the reduction of nitrate and phosphate as well.