Sten Zvorwadza, the leader of a street vendor's union, was charged with insulting or undermining the president in a press interview where he was also quoted as saying that Mugabe was "old" and "day-dreaming".
Zvorwadza is a prominent anti-Mugabe campaigner who has led several demonstrations calling on the veteran leader to step down.
Zimbabwe's worsening economy has seen many people resorting to informal street vending due to massive unemployment.
Zvorwadza is yet to appear in court, the Zimbabwe Lawyers for Human Rights (ZLHR) group said.
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In March, two journalists were arrested over a report that the president, who travels abroad for regular medical treatment, was "in bad shape".
A pastor was also detained after prophesying that Mugabe would die on October 17 this year.
Last week police arrested a journalist who reported that Mugabe's wife Grace had donated second-hand underwear to supporters.
Despite his advanced age and weakening health, Mugabe's ruling ZANU-PF party has endorsed him as its candidate for the 2018 general elections.