This study reports screening of 102 Iranian medicinal plant species belonging to 49 families for the biosynthesis of colloidal silver nanoparticles (AgNPs). Among tested plants, 37 species in 19 plant families are new bio-resources in this regard. Water extracts of macerated plant parts are used in this survey. Six of the bioactive plants are selected for further analysis. They produced amorphous spherical 40-70 nm AgNPs. Biosynthesised colloidal AgNPs are characterised by UV-visible spectroscopy, transmission electron microscopy and scanning electron microscopy. Families of Lamiaceae (8 out of 12), Leguminosae (7 out of 9), Liliaceae (4 out of 7) contained most bio active species. No correlation noticed between bioactivity and pH of plant water-extracts. The simple procedure used in this study may form a platform for mass production of environmentally safe and eco-friendly green production of these multipurpose AgNPs in future; however, optimisation protocols need to be well documented.