Neonatal sepsis remains a major cause of morbidity and mortality in neonates, but signs of neonatal sepsis are nonspecific and blood cultures, although accurate, require a period of incubation before resulting. Therefore, quick, sensitive, and specific non-culture-based diagnostics are needed to improve our ability to diagnose sepsis or—more commonly—to rule it out. A variety of serologic markers (e.g., complete blood counts, C-reactive protein, procalcitonin) and non-serologic tests (e.g., heart rate characteristic monitoring, transcutaneous biologics) have been investigated, but at present, none are an ideal test. This chapter reviews current and future strategies for accurate diagnosis of neonatal sepsis.