Niyonsenga was not present in court and shortly after the verdict, the YouTube star said police had surrounded his home.
Police and prison officials have not confirmed whether Niyonsenga has been taken into custody.
Niyonsenga, better known by his YouTube persona Cyuma, which means "Iron", was known for discussing human rights abuses on his channel.
In April 2020 he broadcast a series of videos accusing soldiers of serious abuses against slum dwellers during the enforcement of a strict coronavirus lockdown.
Shortly afterward, he was arrested and charged with violating the lockdown and impersonating a journalist and sent to prison.
He was acquitted and released 11 months later but prosecutors appealed to a higher court.
His jailing comes weeks after another high-profile critic with a YouTube following was sent to prison.
Yvonne Idamange, a mother of four, was jailed for 15 years in October for inciting violence online.
Aimable Karasira, a university lecturer with a YouTube channel, was arrested in June and charged with genocide denial, a serious crime in Rwanda.
He had accused the Rwandan Patriotic Front, which has ruled the country since 1994 under its leader Paul Kagame, of trampling on human rights.
The crackdown on YouTube creators has had a chilling effect in Rwanda, where independent media has been quashed and other forms of free expression are strictly monitored by the government.
One other YouTuber with a popular following told AFP a government official warned them to stop "this YouTube nonsense or face the consequences".
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