Introduction: Healthcare-associated infections are a public health problem due to the increased morbimortality of patients, even more in patients with risk factors such as those immunosuppressed due to oncological diseases. Knowing the genetic diversity of the main microorganisms causing healthcare infections is important to combine traditional epidemiological surveillance with molecular epidemiology in order to better follow up and detect outbreaks early. Objetives: To determine the phylogenetic group and antibiotic resistance of Escherichia coli isolated from hospitalized oncologic patients. Materials and methods: Cross-sectional study. Sixty-seven strains of extended-spectrum beta-lactamase (ESBL) producing Escherichia coli were included. The phylogenetic group was determined, the antibiotic resistance profile, the betalactam resistance genes, the type of sample and the hospitalization areas from which they were recovered were described. Results: The most frequent phylogenetic group was B2 (36%). 57% of B2 strains were isolated from urine and 33% from the urology department. Resistance to ciprofloxacin and gentamicin were 92% and 53%, respectively, and 79% of the strains had the blaCTX-M gene. A significant association (p<0.05) was found between the phylogenetic groups and ciprofloxacin resistance, and also with age of the patients. Conclusion: The predominant Escherichia coli phylogroup was B2, high resistance to ciprofloxacin and gentamicin, high proportion of BLEE strains with the blaCTX-M gene, and the significant association between phylogenetic group and resistance to ciprofloxacin.