Her husband, Arif Yunus, was given seven years on similar charges. They have been in prison since their arrest nearly a year ago.
Both still face separate charges of treason, which carries a life sentence.
The couple say the case was politically motivated. Azerbaijan has repeatedly jailed human rights activists.
President Ilham Aliyev has ruled Azerbaijan since 2003 and has cracked down hard on political opponents.
Both Leyla, 59, and Arif Yunus are in poor health - she has diabetes and hepatitis C, while he has a heart condition and has suffered two strokes.
US-based Human Rights Watch condemned their prosecution as a "despicable political show trial".
Levan Asatiani, an Azerbaijan researcher at Amnesty International, said "the judicial system has once again revealed itself to be no more than a cynical tool by which President Ilham Aliyev crushes any dissent".
In a statement to the BBC the Azerbaijan government said the court process in the case was "open and free". It also said "the independence of judiciary and the rule of law have been fully guaranteed" in Azerbaijan.
Leyla Yunus was found guilty of fraud, illegal entrepreneurship, tax evasion and falsifying official documents.
She is director of the Institute for Peace and Democracy, a human rights group founded in 1995. It has worked with the Council of Europe - Europe's leading human rights watchdog - and other international bodies, informing them about actions to stifle political dissent in Azerbaijan.
Mrs Yunus had been pressing for reconciliation between oil-rich Azerbaijan and neighbouring Armenia, to defuse their frozen conflict over Nagorno-Karabakh.
Armenian forces took control of the disputed territory in 1994 soon after the break-up of the Soviet Union. But sporadic clashes continue between them and nearby Azeri forces.
(Update 20 August: This article was amended to add the official viewpoint of the Azerbaijan government.)

The head of the mission, Peter Graaff, met the Ghanaian president to thank the country for hosting the agency since it was set up in September last year.
A small team will stay until the end of June to co-ordinate air operations, the agency, known as Unmeer, said.
Ghana has not been affected by the epidemic in West Africa, which has killed more than 11,000 people.
Africa news: Tuesday 9 June as it happens
Why Ebola is so dangerous
Ebola basics: What you need to know
The BBC's Africa health correspondent Anne Soy says the mission set up its headquarters in Accra as it was far enough away from the affected countries, where there was logistical lockdown, but close enough the epicentre of the outbreak.
"By allowing us to set up our headquarter in Accra, President [John ] Mahama demonstrated extraordinary leadership and solidarity," Mr Graaff said in a statement.
"He made Ghana the only open gateway to Guinea, Liberia and Sierra Leone thus allowing the movement of thousands of Ebola responders and medical and essential supplies when they were most needed."
As a result, Unmeer said Guinea, Liberia and Sierra Leone now had the necessary response capabilities in place to efficiently test, treat and isolate Ebola patients.
11,164
Deaths - probable, confirmed and suspected
(Includes one in the US and six in Mali)
4,806 Liberia
3,912 Sierra Leone
2,431 Guinea
8 Nigeria
President Mahama said the downsizing of Unmeer was a sign of success for "short and sharp interventions".
Most of the mission's staff and assets have been moved to Sierra Leone and Guinea, where 24 new cases of Ebola were reported in the last week.
Last month, the World Health Organization (WHO) declared Liberia free of Ebola as the country had had no new cases in 42 days.
The basics: What you need to know
A prominent human rights activist in Azerbaijan, Leyla Yunus, has been sentenced to eight-and-a-half years in prison for fraud and tax evasion.
[NEXT_CONCEPT]
The UN's emergency Ebola response headquarters in Ghana's capital, Accra, is to close as the outbreak slows.