This study was conducted in order to determine the effects of different concentrations of synthesized Fe3O4 nanoparticles (NPs) on the growth, the content of secondary metabolites and antioxidant capacity in Matricaria chamomilla. With this aim, four levels of Fe3O4 NPs concentrations were applied as follows: basic Murashing and Skoog solution (control), 25, 50 and 100 mg L-1 Fe3O4 NPs. The results indicated that the biomass was higher in the plants that were treated with 25 mg L-1 Fe3O4 NPs than the control plants. Biomass was declined in 50 and 100 mg L-1 Fe3O4-exposed plants compared with the unexposed plants. Relative water content was gradually decreased with the enhancement of Fe3O4 concentration. Fe3O4 NPs in 50 and 100 mg L-1 caused a significant induction in number of root. Fe3O4 NPs treatment enhanced production of secondary metabolites such as total phenol and total flavonoid in roots and leaves of M. chamomilla. Moreover, Fe3O4 NPs increased antioxidant ability of the roots and leaves by inducing DPPH scavenging activity at 25 mg L-1 Fe3O4. The results might identify that the application of Fe3O4 NPs can be a useful war for increasing higher content of secondary metabolites in the M. chamomilla plants. Manuscript profile