Acinetobacter baumannii is an opportunistic pathogen notorious for its high prevalence of antimicrobial resistance and cause of hospital-acquired infections, particularly in Intensive Care Units (ICUs). Obesity is a common co-morbidity in ICU patients, and this is associated with increased hospital stays and increased reliance for mechanical ventilation, thereby predisposing the patient to hospital-acquired infections. Importantly, these patients often display dyslipidaemia, characterised by an abnormal circulating level of lipids. Here, we sought to ascertain the efficacy of dietary lipid intervention on influencing the host lipid landscape and its impact on A. baumannii infection. Mice were fed a diet enriched with 5% canola oil, 15% lard, or 15% fish oil for four weeks, followed by intranasal challenge with A. baumannii. Dietary intervention and infection substantially altered host lipid biology, with plasma, lung, and liver lipid fluxes. Spatial lipidomic and pathway analyses revealed that fish oil supplementation led to an inversed lipid homeostatic response to infection. These different lipid landscapes impact on pathogenesis since A. baumannii was able to produce a systemic infection in mice on the canola oil and lard diets, but not in mice fed fish oil. Analyses of A. baumannii isolated from mice on fish oil revealed that this dietary supplement directly impacted on the pathogen's lipid homeostasis and its membrane permeability. Specifically A. baumannii upregulates its fatty acid degradation pathway in an effort to limit the incorporation of polyunsaturated fatty acids into the membrane. Our work shows the effectiveness of dietary change in altering host lipid biology, and the subsequent influences it has on A. baumannii invasion. Specifically, fish oil has protective activity by altered host lipid homeostasis and reducing A. baumannii colonisation. Together, this work has implications for dietary intervention in managing infections in obese and/or dyslipidaemic patients.