Mohammed Haji Sadiq taught for 30 years at Cardiff's Madina mosque and abused four girls as a form of punishment.
He was found guilty of eight sexual assaults on a child under 13 by touching, and six indecent assaults after a trial at Cardiff Crown Court.
The court heard Sadiq, of Cyncoed, "took advantage of his position".
He had denied the charges involving four girls aged between five and 11 and blamed "politics" in the mosque for the accusations.
But sentencing him, Judge Stephen Hopkins QC told Sadiq: "Children called you 'uncle' as a mark of respect.  You are a man in my judgement of some cunning."
He added: "Beneath the veneer there is a dark and deviant side."
Sadiq, who was a part-time Imam, sexually assaulted two girls under the age of 13 by touching, and indecently assaulted two other girls over a decade between 1996 and 2006 at the Woodville Road mosque.
He abused them if they made a mistake while reciting the Koran and would use a stick as a form of punishment in class, hitting people over the hand or hard on the back.
Some of his victims said they were afraid to attend the mosque because of his abuse.
One said she had attempted to take her own life because of the abuse.
In victim impact statements read to the court, others said they felt they could not tell anyone about the abuse because of the culture they grew up in.
The court heard one victim feared the consequences of speaking out following Sadiq's conviction.
She said: "Due to my religion it was very difficult, almost impossible to tell anyone what had happened".
She added: "In the Muslim religion we do not talk about personal matters".
Another victim said it was "not acceptable" in her culture to talk about what was happening at the mosque.
She said: "I remember the relief I felt when I told my mother, and she believed me and went to the police.
"In my family honour is very important, but my family have been very supportive".
Sadiq has had no involvement in the mosque since 2006 when it burnt down and was re-sited elsewhere in the city.
He was cleared of one indecent assault after his trial last month.
In addition to his jail sentence, he was issued with a sexual harm prevention order and will have to register as a sex offender.
Det Ch Insp Rob Cronick of South Wales Police praised the "immense courage" of the victims who came forward.
"As a result of the verdict and today's sentence I believe there may be members of the community who may now feel confident enough to speak to the police or our support agencies," he added.
A spokesman for the children's charity NSPCC said: "This was an appalling breach of trust and Sadiq has rightly received a significant prison sentence for these heinous offences."
A Muslim Council of Wales spokeswoman said: "We applaud the bravery and courage of the young women who now, as adults, pursued the case and pursued justice.
"Mr Sadiq was not an imam but a volunteer teacher at the former Madina Mosque.
"All mosques in Wales now have Child Protection Policies in place, and teachers and volunteers alike are all vetted and closely monitored."

Winger Fenby, 30, a qualified chartered accountant, played for Newcastle and Scarlets before joining Irish in 2013.
Former Harlequins back-row Guest, 31, brings a 14-year playing career to a close having won the Premiership, European Challenge Cup and LV= Cup.
Injuries restricted him to just two Premiership starts this season, his second with London Irish.
Fenby scored two Premiership tries this term as well as a hat-trick against Edinburgh in the European Challenge Cup pool stage.
"I have really enjoyed my time with London Irish and it's with a heavy heart I've come to make this decision and pursue a new opportunity," he said.
Guest made more than 200 appearances for Quins and scored three times for the Exiles and admitted retirement was a tough decision to take.
"There are a lot of experiences that will live long in my memory, and I am grateful to have played rugby at the highest level for many years," he added.
An 81-year-old former Koran teacher who was convicted of a string of child sex offences has been jailed for 13 years.
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London Irish players Andrew Fenby and Tom Guest have announced their retirement from professional rugby.