Tens of thousands of would-be students were congratulated by Ucas for accepting teacher training places - even when they had not applied.
The university admissions service wrongly sent an email to everyone who has applied to study undergraduate degree courses next year - understood to be more than 61,000 applicants.
The error, made on Tuesday morning, was picked up within 15 minutes, and a second email apologising for the mistake was sent out within half an hour, Ucas said.
Many students who received the email took to social media to express their shock and amusement at the error, first reported by the Times Educational Supplement (TES).
Ucas used the social media site to issue an apology, tweeting: "We're sorry if you received an email about being accepted for a UCAS Teacher Training programme, these were sent in error."
In response, one Twitter user, @hanmowbray wrote: "Thank God you gave me a heart attack."
Helen Thorne, Ucas director of external relations, said the mistake had been picked up quickly by the customer experience and marketing team and an email apology sent to those affected.
"We would like to reassure university applicants that their applications have not been affected in any way by this," she said.
"Anyone who was sent this message who has not applied to become a teacher should simply ignore it."