Background: Plant-mediated synthesis of silver nanoparticles provides a sustainable route to antimicrobial nanomaterials, while antibiotic functionalization may enhance activity against clinically relevant bacteria. This study evaluated Artemisia maritima-mediated AgNPs and their functionalization with ampicillin. Methods: Aqueous A. maritima extract was used to synthesize AgNPs, followed by ampicillin functionalization. Phytochemical screening, UV-Vis spectroscopy, FTIR, X-ray diffraction, temperature- and time-dependent UV-Vis analysis, and antibacterial testing against five bacterial pathogens were performed. Results: Surface plasmon resonance peaks occurred at 401 nm for AgNPs and 457 nm for AMP-AgNPs, supporting nanoparticle formation and surface functionalization. XRD showed characteristic crystalline peaks at 2θ values of 27°, 32°, 38°, 44°, and 64°, while FTIR identified hydroxyl (3262.54 cm⁻¹), aromatic C=C (1507 cm⁻¹), and amine-related C-N (1023.07 cm⁻¹) groups. At 10 μg/mL, AMP-AgNPs produced inhibition zones of 34 mm against Escherichia coli, 32 mm against Pseudomonas aeruginosa, and 31 mm against Klebsiella pneumoniae, exceeding the activity of non-functionalized AgNPs. Conclusion: Artemisia maritima-derived AgNPs were crystalline, phytochemical-capped, and successfully functionalized with ampicillin. Their enhanced antibacterial activity supports further investigation as antimicrobial nanomaterials, with future work requiring standardized susceptibility testing, particle-size analysis, and mechanistic validation.