Background: The limited pipeline of new antibiotics has increased interest in antimicrobial peptides (AMPs) as adjuvants that can enhance the activity of existing agents. Novel AMPs previously identified through metagenomic bioprospecting of hydrocarbon-contaminated Nigerian soils were evaluated for their ability to potentiate meropenem. Methods: A standard broth microdilution checkerboard assay was performed with the synthesised peptides ZB4 and ZB8 in combination with meropenem against A. baumannii S26063. Two-fold serial dilutions of each agent were prepared in 96-well plates. Bacterial growth was quantified by optical density at 600 nm (OD₆₀₀) after incubation. Minimum inhibitory concentrations (MICs) of the agents alone and in combination were determined, and interactions were quantified using the fractional inhibitory concentration index (FICI). All experiments were performed in three independent biological replicates. Results: Meropenem alone exhibited an MIC of 0.25 µg/mL, while ZB8 showed limited intrinsic activity (MIC 128 µg/mL). The combination of ZB8 and meropenem produced strong synergy, with a minimum FICI of approximately 0.016. Effective growth inhibition was achieved at 0.016 µg/mL ZB8 and 0.004 µg/mL meropenem, corresponding to an approximately 8,000-fold reduction in the required concentration of ZB8 and a 64-fold reduction in the concentration of meropenem relative to their respective solo MICs. In contrast, ZB4 exhibited no measurable activity up to 128 µg/mL, precluding formal FICI calculation. Conclusion: ZB8, a novel AMP derived from oil-contaminated soil metagenomes, potentiates meropenem and enables dose sparing against A. baumannii, supporting the development of derived AMPs as antibiotic adjuvants against clinically relevant pathogens.