ABSTRACT Background: To assess the prevalence of Acinetobacter calcoaceticus–baumannii complex [Acb complex] and non-Acb strains from the urine samples of elderly population with urinary tract infection (UTI) by both phenotypic and genotypic (PCR) characterisation methods from India. Methods: A longitudinal cohort study on 1000 elderly population with UTI was performed for a period of 1 year. Using standard microbiological guidelines, the urine samples were cultured and the Acb and non-Acb complex were identified by standard biochemical characterisation tests. DNA was extracted from all the phenons of the complex for further confirmation by PCR. The amplicons were sequenced for the phylogenetic analysis and clonal identification by comparative genomic assessments. Results and conclusions: Study population yielded 8.5% of Acb and non-Acb-complex with other gram-negative pathogens ranging from 1 to 49.3%. Males were highly affected with the complex under the age group of 70–90. Statistics of the demographic data within the groups showed significant results of the prevalence of Acb and non-Acb complex towards the age group selected and with other associated co-morbidities recorded (at p < 0.05). Chi2 statistics for the goodness of fit was significance for genotypic confirmation of the complex. Conclusions: The present investigation documents the prevalence of the Acb and non-Acb complex among the elderly population and suggests the implementation of phenotypic and molecular strategies to assess the correct prevalence rate of the same for surveillance which will also aid in the effective clinical management of UTI by Acb and non-Acb-complex in elderly population.