This study was aimed at investigating the prevalence of hyponatremia in patients with intracapsular femoral neck fracture. All records containing clinical and laboratory information of patients admitted with femoral neck fractures to the Academic Hospital of Parma (Italy) during the year 2013 were retrieved from the hospital database. The control population consisted of subjects admitted to the outpatient phlebotomy center during the same period. The final population consisted of 543 patients with femoral neck fractures and 700 outpatients. The category of elderly subjects (i.e., ≥65 years) included 491 patients and 380 controls. In both the entire population and elderly subjects, serum sodium was lower in patients than in controls (138 versus 139 mmol/L, P<0.001). The prevalence of hyponatremia was also higher in cases than in controls, both in the entire population (19.5 versus 10.4%, P<0.001) and in elderly subjects (20.8 versus 11.8%, P<0.001). The odds ratio of hyponatremia for femoral neck fracture was 2.08 in the entire study population and 1.95 in those aged 65 years and older. In conclusion, we found that hyponatremia is significantly associated with femoral neck fracture. Serum sodium should hence be regularly assessed and hyponatremia eventually corrected.