The seven seminarians were initially barred from the City Arms in Cardiff on Saturday despite insisting their clothes were not fancy dress.
— The City Arms (@cityarmscardiff) July 29, 2017
But they managed to get their celebratory pints on the house after the bar manager realised they were the real thing.
Father Michael Doyle said the seven went to the pub in Quay Street to celebrate the ordination of Father Peter McLaren at Cardiff Metropolitan Cathedral of St David near Queen Street.
He said it was a double celebration because Fr McLaren was the second to be ordained to the priesthood in a week.
He added that the City Arms was a favourite of his colleagues including the Archbishop of Cardiff, George Stack.
Fr Doyle said: "They arrived at the City Arms and they were dressed wearing the clerical collar.
"The doorman basically said something along the lines of, 'sorry gents, we have a policy of no fancy dress and no stag dos'."
The doorman was good-natured but firm, and the students had started to leave when they were approached by the bar manager.
"He basically said, 'you're real, aren't you?'," said Fr Doyle.
"He invited them back in and when they walked back in the entire pub burst into a round of applause, and they had a free round off the City Arms."
Fr Doyle said the group stayed in the pub most of the afternoon chatting to locals, and also discovered that one of them shares the name of one of Brains brewery's most popular ales.
He said: "Reverend Rob James decided to buy the barman a drink and, of course, one of the Brains beers in Wales is the Reverend James, so the Reverend Robert James bought a Rev James for the barman."
City Arms assistant manager Matt Morgan said: "At first one of our staff members thought the group were a stag party in fancy dress and suggested they might want to try another pub, as we generally have a quieter crowd of drinkers than others nearby.
"When we realised our mistake we quickly apologised to the priests and thankfully they were all great sports and saw the funny side of the situation.
"It's not every day you have a group of priests drinking in the pub and they would be welcome back any time."
Fr Doyle said such mix-ups were not uncommon and a drinker in another Cardiff bar had asked the group whether they were a stag do the previous weekend.
He added that the incident was "funny" and "just gold" and that the seminarians had not been put off returning to the pub.
Archbishop Stack said: "It is wonderful to hear that the seminarians were celebrating their own path to priesthood by having a good time in Cardiff, which of course they are allowed to have.
"The diocese is celebrating the ordination of two seminarians in a week despite rumours about the shortage of men presenting themselves for priesthood.
"Priests are part of the community and for the community they serve.
"I would like to add that the Rev Robert James does not have any shares in the brand of beer which shares his name."