Simon Bridges - or someone working for him - made a boo-boo on photo-sharing site Instagram on Friday.
They posted a photo of the new National leader with a draft caption, seeking the go-ahead to use it.
"Brilliant! Posting that now - this caption ok?" Mr Bridges' post read. "On a road trip to Whanganui today to give a speech so had to make a quick pit stop for the obligatory photo in Bulls."
Mr Bridges or his employee later amended the caption, or posted the photo again - it's not clear which - with the caption, which had obviously been approved.
"Yes the caption is ok," the first comment read.
"Unbelievea-bull mate," added fellow National MP Chris Bishop.
The faux pas was quickly mocked on rival social site Twitter.
"Tweets on Winston Peters NZ politician," wrote Tim McCready, referencing the New Zealand First leader's infamous Twitter mistake of 2017.
The photo showed Mr Bridges standing with a statue of a bull.