The social media giant said the tweet violated the company’s “civic and election integrity” rules.
The US president had tweeted: “So now the Democrats are using Mail Drop Boxes, which are a voter security disaster. Among other things, they make it possible for a person to vote multiple times.
“Also, who controls them, are they placed in Republican or Democrat areas? They are not Covid sanitized. A big fraud!”
The tweet has now been hidden behind a “public interest” notice and Twitter users can no longer like, reply or retweet Mr Trump’s comments.
“This tweet violated the Twitter rules about civic and election integrity,” the notice says.
“However, Twitter has determined that it may be in the public’s interest for the tweet to remain accessible.”
A statement shared on the Twitter Safety account said the “misleading health claims” could “dissuade people from participation in voting”.
“Per our policies, this tweet will remain on the service given its relevance to ongoing public conversation,” it said.
“Engagements with the tweet will be limited. People will be able to retweet with comment, but not like, reply, or retweet.”
One of Mr Trump’s tweets was first given a fact-check label by Twitter in May.
Twitter’s civic integrity policy states: “You may not use Twitter’s services for the purpose of manipulating or interfering in elections.
“This includes posting or sharing content that may suppress voter turnout or mislead people about when, where, or how to vote.”