Prosecutors said the group attacked an office of the ruling ZANU-PF party, in Nyatsime, south of the capital, last week.
The ruling ZANU-PF party has been in power since independence in 1980.
The group "destroyed several houses and also assaulted members of the Nyatsime community thereby causing massive destruction to property and inflicted serious injuries on them," prosecutors said.
The incident comes as rights groups and opposition parties have complained of a clampdown ahead of the vote.
Lawyers for those detained however stopped short of saying the accusations were politically motivated.
"Our clients were not even at the scene," Anesu Chirisa, legal lead at Zimbabwe Human Rights NGO Forum, an umbrella group representing the 39 told AFP.
The 39 were arrested over the weekend and on Monday briefly appeared before a local court.
They were remanded into custody after investigating authorities called for a "lengthy custodial sentence."
The group are supporters of the Citizens Coalition for Change, Zimbabwe's leading opposition party.
CCC's leader Nelson Chamisa, a 45-year-old lawyer and pastor, is hoping to replace President Emmerson Mnangagwa, 80, who is seeking a second term in the August 23 vote.
Analysts are bracing for a tense ballot in a country where discontent at entrenched poverty, power cuts and other shortages runs deep.
Critics have accused the government of using the courts to target opposition politicians and say there has been an increase in arbitrary arrests and repression.
Earlier this month another five CCC activists were held on various charges including assault after an alleged altercation at a voter registration centre.