Familial neurohypophyseal diabetes insipidus (FNDI) is a genetic disorder presenting with polyuria and polydipsia and is caused by mutations in the arginine vasopressin-neurophysin II (AVP-NPII) gene. The clinical manifestations of this disorder vary greatly depending on different mutations. The present study reports the genetic, clinical and biochemical characteristics of patients with FNDI caused by five novel mutations. Ten patients encompassing two pedigrees and four individual cases diagnosed with FNDI were included. Biochemical markers and magnetic resonance imaging (MRI) were evaluated and genomic DNA was sequenced. The results revealed that age at onset ranged from 1.0 to 11.0 years. Daily urine volumes ranged from 2.0 to 12.0 liters. One patient had mental retardation and three patients had puberty retardation; one patient had nausea, vomiting and mental retardation; and two patients had fever. Treatments, if given, included desmopressin and vasopressin tannate. Posterior pituitary T1-weighted MRI high-intensity signals were absent in two cases and present in four cases. Sequencing revealed five novel mutations in the AVP-NPII gene. On the whole, the findings of the present study indicate that FNDI exhibits different clinical manifestations and a diverse age at onset. Posterior pituitary MRI does not provide a definite diagnosis of FNDI. We also identified five novel AVP-NPII mutations. Thus, an enhanced understanding of FNDI pathogenesis may provide a basis for the development of presymptomatic FNDI diagnotic tools.