The aim of the present study was to examine the effect of an acute increase in cortisol in response to a psychosocial stressor on heartbeat perception, in a laboratory environment. Thirty-six participants (20 women, 16 men, mean age = 21.7 years, standard deviation = 1.7 years) completed a heartbeat counting task (Schandry paradigm) before and after exposure to an acute psychosocial stressor (Trier Social Stress Test; TSST). Heartbeat counting performance was compared between participants who exhibited strong cortisol responses (>15.5% increase in cortisol from baseline; responders) and those who did not (non-responders). Responders showed increased heartbeat counting accuracy following the TSST, which was not observed in non-responders. The two groups did not differ in their responsivity to subjective anxiety ratings or heart rate. These results indicated that acutely elevated cortisol in response to a psychosocial stressor is associated with increased interoceptive accuracy. The results provide a possible explanation for inconsistent findings on the effect of stress exposure on interoception.