OBJECTIVE To identify whether therapeutic hypothermia in newborns with hypoxic ischemic encephalopathy affects gentamicin pharmacokinetics. STUDY DESIGN Retrospective case-control study consisting of 16 neonates who underwent therapeutic hypothermia and received gentamicin with interpretable peak and trough serum levels obtained during the period of cooling and at steady state; comparator group consisting of 7 neonates met the criteria but did not undergo therapeutic hypothermia. RESULTS Significant differences in gentamicin pharmacokinetics were noted between the therapeutic hypothermia group and the comparator group in elimination rate constant (0.08/h versus 0.11/h; P < 0.01), elimination half-life (9.16 hours versus 6.56 hours; P < 0.01), and clearance (0.04 L/kg.h(-1) versus 0.05 L/kg.h(-1); P < 0.01), respectively. Higher gentamicin trough serum concentrations were seen with the therapeutic hypothermia group (1.68 mcg/mL versus 0.77 mcg/mL; P < 0.01). CONCLUSIONS Therapeutic hypothermia is associated with alterations in gentamicin pharmacokinetics, reducing gentamicin clearance by 25.5% in neonates with hypoxic ischemic encephalopathy, which may result in increased trough serum concentrations.