Last week, Mr. Kudlow floated the possibility of dividing NAFTA talks and cutting separate bilateral deals with Canada and Mexico.
Kudlow joined Trump's administration as the president's top economic adviser in March, replacing Gary Cohn.
Kudlow's condition wasn't immediately released by Walter Reed National Military Medical Center in Bethesda, Maryland.
"Our Great Larry Kudlow, who has been working so hard on trade and the economy, has just suffered a heart attack", Trump tweeted Monday evening, US time. Appearing on CNN's "State of the Union" show on Sunday, Kudlow called Trudeau's criticism of Trump's tariff proposals "a betrayal" that "really kind of stabbed us in the back".
Kudlow served in the Reagan administration and was a high-flying Wall Street executive in the 1990s, before undergoing treatment for drug and alcohol problems.
With Trump's tax cuts already being implemented, Kudlow has been advising a president who pushed to tax foreign imports - a policy Kudlow personally opposes.
There was no additional information from the White House or second source, rather it was only Trump's twitter account.