Mr Gove said farmers and food producers faced “considerable turbulence” if the UK leaves the EU with no deal.
He told the Oxford Farming Conference it was a “grim and inescapable fact” there would be tariffs on exports and new sanitary and other border checks.
While “not perfect”, he said Theresa May’s Brexit deal would protect market access and provide economic certainty.
Responding to his remarks, Martina Anderson said: “The admission by the British government’s environment secretary, Michael Gove, that Brexit will be turbulent for farmers must surely be in line for understatement of the century.
“He warned delegates at a farming conference that the consequences will be particularly felt by smaller farms, typically family farms.
“The fact is that Brexit will be disastrous for the farming and agriculture sectors in the north where there are more smaller farms.
“It will decimate small farms and put the livelihoods of many in jeopardy.
“Of course, the Tories have shown time and time again that they don’t care about the impact of Brexit on people in the north.
“As the Irish government steps up its plans for a no deal Brexit it must ensure that the needs of the Irish agriculture sector north and south are taken into consideration,” added the MEP.