Background: Cyanobacterium-based silver nanoparticles are considered not only as an efficient nano-nematicide but also as a bio-stimulant material for plant growth. They could be employed as a part of an integrated program for controlling some plant diseases.Results: In this study, silver nanoparticles (Ag-NPs) were biosynthesized from aqueous extract of the cyanobacterium,Nostocsp. PCC7524. Full characterization of the biosynthesized Ag-NPs was monitored by UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction pattern, Zeta sizer, and Fourier transform infrared spectroscopy. In vitro assay against the root-knot nematodeMeloidogyne javanicashowed that Ag-NPs significantly decreased egg hatching ofM. javanicaat different applied concentrations (3, 6, 12, 25, and 50%, v/v). Fifty percent of Ag-NPs induced the highest reduction percent (94.66%). Moreover, Ag-NPs and AgNO₃significantly increased the percentages of larval mortality of the second-stage juveniles (J₂) with concentration and time-dependent responses. Ag-NPs or AgNO₃at 2.4 ml/l, 24 h, completely inhibited the growth of J₂compared to 23% inhibition using aqueous cyanobacterial extract (ACE). In vivo effect of Ag-NPs on faba bean-infected plant under greenhouse conditions was achieved by treating soil with three different concentrations of 1, 2, and 3 ml/kg soil over two consecutive seasons. Ag-NPs significantly reduced root galling from 39.6 to 78.7% and J₂population in the soils from 32.2% to 86.7% in the 2018 season and from 21.9 to 78.1% and 40.0 to 81.0% in the 2019 season, respectively. Moreover, 3 ml/kg soil of Ag-NP treatment showed statistically comparable effects to that of vydate nematicide but with remarkable enhancement of faba bean growth parameters as compared to those of vydate or AgNO₃treatments in the two seasons.Conclusions: The considerable in vitro and in vivo nematicidal potential of the cyanobacterium-based Ag-NPs, besides their bio-stimulant effect on plant growth, makes them feasible for the biological control ofM. javanica.