Presenting a segment on fisherman's jumpers, the presenter sent Twitter into a frenzy as he presented from a seemingly chilly location.
Viewers flocked online to comment on the "distressing" visual which saw the 76-year-old flash a little more than he had intended.
Despite being dressed in a chunky grey jumper with another top underneath, John's nipples were impossible to miss during the winter special from Filey in Yorkshire.
As he stood on the east coat, the star reassured people at home: "It's a tight knit, and certainly a bit of a tight fit but it does feel incredibly warm this jumper on a bitterly cold day.
Countryfile: John Craven caused quite a stir on Twitter last night
Countryfile: John Craven's nipples were impossible to miss
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Wed, October 26, 2016
Countryfile controversies: We look at the most shocking moments on the popular rural show.
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It's a tight knit, and certainly a bit of a tight fit!
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"And, ways of keeping ourselves warm in winter time has certainly come a long way since the gansey."
One shocked Countryfile fan tweeted: "Watching John Craven trying to convince the viewer that his jumper is warm with nipples that could cut glass #countryfile."
Two others continued: "Oh no… Nips on show… And they're John Cravens #countryfile," and: "John Craven nip slip #countryfile."
Countryfile viewers flocked to Twitter to comment on John Craven's 'nip slip'
Countryfile: John Craven was presenting a segment on fisherman's jumpers
"@BBCCountryfile do we get to see John Craven's nipples/moobs again next week? Distressed. He's a father figure #countryfile," a fourth went on.
The micro-blogging site was flooded with remarks about his over-share, including: "I'm admiring John Craven's perky nipples on #countryfile tonight, pressing coquettishly against his fisherman's sweater."
Countryfile continues next Sunday at 7pm on BBC One.