Neonatal Sepsis (NS) is a systemic infection caused by bacteria, fungi, or viruses during the first month of life. Although various studies have identified the factors associated with NS, it is a public health problem due to its high morbidity and mortality. The study aimed to identify the risk factors associated with neonatal sepsis in the Neonatal Intensive Care Unit (NICU) of a tertiary hospital in Mexico. A case-control study was carried out using records of neonates (with sepsis 39 and without sepsis 39) from January to December 2017. The risk factors studied were the sociodemographic and clinical characteristics of the mother and clinics of the neonate. The data were analyzed using the Chi2 test, Fisher's exact test, Student's t-test, and the Odds Ratio (OR). The risk factors associated with NS were gestational age (OR 0.77, CI 95% = 0.64-0.91, p = 0.004), newborn weight (OR 0.45, CI95% = 0.23-0.86, p = 0.017) and days of hospital stay (OR 1.06, CI95% = 1.02-1.10, p = 0.0014). The mother's sociodemographic and clinical factors were not associated with NS. Risk factors associated with NS were gestational age, newborn weight, and days of hospital stay.