The judge said a lower court had erred in denying Ngarivhume bail. Another judge will rule on whether to free Chin'ono later on Wednesday.
As part of bail conditions, Ngarivhume, who leads a small opposition party, Transform Zimbabwe, was barred from posting on Twitter until his case is finalised, must surrender his passport to the court and report to the police three times a week.
Prevented from protesting by restrictions the government says are needed to stop the spread of Covid-19, activists have used a Twitter hashtag #ZimbabweanLivesMatter to criticise President Emmerson Mnangagwa and encourage global pressure on his government.
When Chin'ono made a routine court appearance on Tuesday, he looked visibly frail and told reporters that he was unwell and doctors had taken a sample to test for Covid-19.
The detention of Ngarivhume and Chin'ono and arrest of dozens of activists has led to accusations that the government is persecuting the opposition, a charge the authorities deny.
The opposition has disputed Mnangagwa's 2018 election, which took place after he replaced ruler Robert Mugabe in a coup, promising a break with Mugabe's authoritarian style.