Background:Artemisia sieberi(mugwort) is a member of the daisy family Asteraceae and is widely propagated in Saudi Arabia.A. sieberihas historical medical importance in traditional societies. The current study aimed to assess the antibacterial and antifungal characteristics of the aqueous and ethanolic extracts ofA. sieberi. In addition, the study investigated the effect of silver nanoparticles (AgNPs) synthesized from theA. sieberiextract. Methods: The ethanolic and aqueous extracts and AgNPs were prepared from the shoots ofA. sieberi. The characteristics of AgNPs were assessed by UV–visible spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and dynamic light scattering (DLS). The antibacterial experiments were performed againstStaphylococcus aureus,Bacillus subtilis,Escherichia coli, andPseudomonas aeruginosa. The fungal species used wereCandida parapsilosis,Candida krusei,Candida famata,Candida rhodotorula, andCandida albicans. The antibacterial and antifungal characteristics were evaluated by measuring the diameter of growing organisms in Petri dishes treated with different concentrations of either extracts or AgNPs compared to the untreated controls. Furthermore, TEM imaging was used to investigate any ultrastructure changes in the microbes treated with crude extracts and AgNO3. Results: The ethanolic and aqueous extracts significantly decreased the growth ofE. coli,S. aureus, andB. subtilis(p< 0.001), whileP. aeruginosawas not affected. Unlike crude extracts, AgNPs had more substantial antibacterial effects against all species. In addition, the mycelial growth ofC. famatawas reduced by the treatment of both extracts.C. kruseimycelial growth was decreased by the aqueous extract, while the growth ofC. parapsilosiswas affected by the ethanolic extract and AgNPs (p< 0.001). None of the treatments affected the growth ofC. albicansorC. rhodotorula. TEM analysis showed cellular ultrastructure changes in the treatedS. aureusandC. famatacompared to the control. Conclusion: The biosynthesized AgNPs and extracts ofA. sieberihave a potential antimicrobial characteristic against pathogenic bacterial and fungal strains and nullified resistance behavior.