Outside court in the capital, Kigali, the 55-year-old politician said: “I don’t agree with what the judge said, and unfortunately you can’t appeal before two years.
“We are still far from a law-abiding country.”
Ms Ingabire is an outspoken critic of President Paul Kagame, who has been the dominant force in the country for three decades.
He secured more than 90% of the votes in presidential elections in 2003, 2010 and 2017 – and changes to the constitution mean he could potentially stay in power for another 10 years.
The 66-year-old president has faced criticism from rights groups, which have accused him of cracking down on the opposition.
But Mr Kagame has in the past fiercely defended Rwanda’s record on human rights, saying his country respects political freedoms.
There is currently only one challenger to the president in July’s election in the shape of the Green Party’s Frank Habineza, the AFP news agency reports.
He won 0.45% of the vote in 2017.
In 2010, Ms Ingabire returned from exile in the Netherlands to take part in that year’s presidential election.
But she was arrested, prevented from standing and later sentenced to 15 years in prison. After she was pardoned in 2018, she went on to found the Dalfa-Umurinzi opposition party.
Ms Ingabire, a member of the majority Hutu ethnic group, had got into trouble for questioning why Rwanda’s official memorial to the 1994 genocide did not include any Hutus.
Most of the 800,000 people killed in the space of 100 days were ethnic Tutsis but Hutu moderates were also slaughtered by the Hutu extremists.
Mr Kagame’s Tutsi-dominated Rwandan Patriotic Front (RPF) rebel group – now a political party – ousted the regime behind the genocide and has been in power ever since.