Thromboses are infrequent but serious complications of patients in the NICU. Thromboses tend to occur in very sick neonates, particularly preterm neonates, and the majority of such thromboses are related to central vascular catheters. Other risk factors for neonatal thromboses include infants of diabetic mothers, sepsis, small for gestational age, congenital heart disease, maternal antiphospholipid syndrome, and possibly inherited prothrombotic disorders. Appropriate treatment, dosage, and duration of therapy for neonatal thromboses has not been studied in clinical trials. Treatment options include observation, anticoagulation, thrombolysis, and surgical thrombectomy. Regardless of the treatment chosen, all neonates with thromboses require frequent reassessment of the thromboses by angiography, echocardiography, or ultrasound until thrombus resolution occurs.