Neonatal sepsis contributes significantly to neonatal morbidity and mortality and is a major public health challenge around the world. Depending on the mode of occurrence, a distinction is made between maternal-transmitted infection and that acquired in the postnatal period. Although the etiologies maternally transmitted diseases are well understood, those of postnatal acquired infections are variable depending on the epidemiology of each hospital environment. On the one hand, risk factors for maternal-transmitted infections are maternal sepsis, prolonged premature rupture of membranes, chorioamnionitis, and bacteriuria in the mother during pregnancy. On the other hand, risk factors for postnatal acquired infections are prematurity, low birth weight, lack of hygiene, and invasive therapeutic interventions. The diagnosis is based on a series of anamnestic, clinical and biological features. Although the positive diagnosis is based on the isolation of the germ by culture on a body sample (blood, cerebrospinal fluid, urine, etc.); its low sensitivity leads to the use of markers of the acute phase of inflammation such as C-reactive protein, procalcitonin and interleukins. New molecular biology techniques are promising and offer precise diagnosis with rapid results. Empirical management is a function of microbial ecology while definitive treatment is guided by the results of microbial culture. This article presents the essential elements for understanding neonatal sepsis and discusses new diagnosis and therapeutic management. It offers a thorough reading based on the issue of infections in newborns.