Antibiotic-resistant bacteria are becoming a serious threat to public health worldwide. To address this problem, we have developed multifunctional peptide (MFP)-coated silver nanoparticles (MFP@AgNPs) for antibacterial studies. MFPs, which can physically adsorb to AgNPs via electrostatic interactions are comprised of a matrix metalloproteinase (MMP) cleavable sequence (PVGLIG), an antimicrobial peptide (tachyplesin-1), and a target peptide (PGP-PEG). The resulting MFP@AgNPs were characterized by various technologies, including UV-vis spectrophotometry, zeta potential analyzer, circular dichroism (CD) spectroscopy, attenuated total reflection-Fourier-transform infrared spectroscopy (ATR-FTIR), and transmission electron microscopy (TEM). The MIC and MBC were investigated against both Gram-positive bacteria and Gram-negative bacteria. The antibacterial activity in vivo was evaluated on MDR-AB (multidrug-resistant Acinetobacter baumannii) infected mice. We found that MFP@AgNPs exhibited antibacterial activity against both Gram-positive bacteria and Gram-negative bacteria. Compared to bare AgNPs, MFP@AgNPs-1 killed MDR-AB faster and more efficiently. SEM images showed that MFP@AgNPs-1 induced cell disruption via cell membrane damage. In vivo studies further confirmed the enhanced antibacterial activity against MDR-AB infections. The developed MFP@AgNPs-1 reduced the cytotoxicity of AgNPs and enhanced the antibacterial activity against MDR-AB in vitro and in vivo, providing a possible solution against multidrug-resistant bacterial infections.