Silver nanoparticles (Ag NPs) were incorporated with a uniform alginate polymer matrix for developing the Alginate-Ag composite.  The surface morphology of the nanocomposite was examined by scanning electron microscopy (SEM). The optical characteristics of the nanocomposite were investigated by photoluminescence (PL) and UV-Vis absorption measurement. The study showed that the AgNPs were well-dispersed into the matrix of alginate, the integrated nanoparticles had a size ranging from 7 - 66 nm, and had an average size of about 20.8 nm, and there was aggregation of AgNPs into small clusters. The UV-Visible spectrum showed absorption with a maximum value of 410 nm. The Alginate-Ag nanocomposite demonstrated strong antagonistic properties against the fungi A. niger with inhibition rates of 100, 200 ppm at 73.01%, and 87.41%, respectively.