Acinetobacter baumannii and Klebsiella pneumoniae are important nosocomial pathogens commonly associated with drug resistant infections. They have been reported as co-existing in single polymicrobial infections. Their co-existence is likely underreported clinically but concerningly, their virulence properties and antibiotic resistance profiles may differ as compared to those of single species. In this study, we performed genomic, phenomic, transcriptomic and physiological analysis of isolates from a dual-mixed-species infection and characterised their interactions both in vitro and in vivo. Phenotypic microarrays revealed higher metabolic flexibility of the K. pneumoniae strain compared to A. baumannii. Specialized co-culture assays, HPLC analysis and cross-feeding dynamics revealed that K. pneumoniae metabolites supported growth of A. baumannii under certain conditions. RNA-seq analysis of co-cultures vs pure cultures (grown in biofilms) supported our cross-feeding observations: an increase in ethanol utilisation genes in A. baumannii and increased fermentation genes in K. pneumoniae. Mixed growth in biofilms resulted in increased expression of stress response genes and reduced expression of cell division genes in K. pneumoniae. Microscopic examination of co-culture biofilms with SEM suggested that these strains can co-localize within biofilms, with observations of increased elongated cell morphology, as compared to single strain biofilms. We tested the virulence of both strains as single infections vs coinfections in the Galleria mellonella in vivo model and found that larvae with K. pneumoniae single infections had half the survival rate of A. baumannii single infections. Interestingly, coinfection with both strains had less survival of larvae per cell injected. This work highlights the importance of studying ESKAPE pathogens in the context of polymicrobial communities as their interactions can provide useful insight into treatment of bacterial coinfections.