Refeeding syndrome is a life-threatening clinical disorder that can occur when treating malnutrition. The aim was to examine the current knowledge of refeeding syndrome in patients ≥ 65 + years with special focus on the incidence of hypophosphatemia (HP) in relation to refeeding rate (kcal/kg/day), number of days until the lowest level of phosphate occurs (day of nadir), refeeding rates and adverse events, and death. Specifically, we hypothesized that higher energy provision would cause a higher incidence of HP. A search was conducted in the available databases. Two cohort studies, 1 case control, and a total of 12 case series/case reports, which accounted for 19 individual patient cases, were eligible. The incidence of HP (<0.5 mmol/L) was 15% and 25% in the 2 cohort studies and 4% in the case control study. The mean day of nadir was between days 2 and 3 in the cohort studies, day 11 in the case control study, and day 3 in the cases series/case reports. Importantly, a rapid drop in phosphate occurred receiving both 30 kcal/kg/day and 8 to 10 kcal/kg/day. The cohort studies reported high death rates—26% and 23%—using both 10 and 20 kcal/kg/day, respectively. Adverse events were noted in most all case series/case reports. Clinicians should be aware that HP may occur in up to 25% of older hospitalized adults, and importantly, it occurs even when refeeding cautiously. Hence, electrolytes should be closely monitored, especially between days 2 and 4, which is when the day of nadir occurs most frequently.