The Latin American nation imports billions of dollars' worth of the yellow grain from the United States to feed its livestock.
But with Trump pushing to shake up the countries' trade ties, Mexico is now threatening to buy from elsewhere.
That is worrying corn growers in some of the very same US states that voted heavily in favor of Trump: Iowa, North Dakota, Kansas, Missouri and Nebraska.
Trump has vowed to restrict free trade with Mexico in order to protect US jobs and industry.
But with Mexico gearing up for a potential trade battle, the effect could be the opposite -- at least when it comes to corn.
"For US corn producers, Mexico is their number one export customer," Thomas Sleight, president of the US Grains Council, told AFP.
"They are concerned about maintaining excellent relationships with long standing customers that they've built over generations."