Error-related negativity (ERN) is observed immediately after an error in choice reaction time tasks performed by hand response. We examined whether the ERN occurs in relation to slips of vocalization in the Stroop color word task. In one condition, the subject's vocal responses were masked by continuous pink noise in order to prevent vocalization-related cortical potentials from contaminating the ERN time window. This masking procedure was successful in inhibiting the vocalization-related cortical potential. More importantly, vocalization errors elicited a frontocentral negative-going deflection followed by a positive component immediately after the error response regardless of the masking condition. The present results suggest that the error detection mechanism may also elicit an ERN-like component in response to vocal slips.