McDonald's spokeswoman Terri Hickey said: "Based on our investigation, we have determined that our Twitter account was hacked by an external source".
McDonald's did not immediately respond to a request from the Globe for comment on the tweet, but the company posted a follow-up message saying its account had been "compromised".
The McDonald's tweet was removed from the account, which has 154,000 followers, several minutes later but not before the hashtag #BoycottMcDonalds began. It also poked fun at the size of Trump's hands.
Trump's list of online enemies keeps on growing, with his latest potential foe being popular, fast-food chain McDonald's.
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"Together, Grimace, we could own this town", Trump says to the creature, embracing him as they look over New York City from Trump Tower.
While fans of Mr. Trump's may not have been amused, some experts said the tweet could actually help boost McDonald's standing. When McDonald's calls itself a "modern, progressive burger company", what it means is that it hopes to "lure back customers" by selling superficially higher-end products for low prices.
Trump, who has not made any secret of his love for McDonald's fast food, has been somewhat of a free advertisement for the restaurant chain in the past.
It remains to be seen how the account was compromised. "I like cleanliness, and I think you're better off going there than maybe some place that you have no idea where the food is coming from".
"As long as Trump doesn't tweet at them directly, which could be pretty disastrous, this will be a short-term thing for them", Mike Froggatt, director of intelligence at L2, told Reuters.