Zameer Ghumra, who showed a beheading video to a child, has been convicted of disseminating “terrorist propaganda”.
The pharmacist showed the boy a graphic Twitter video on his mobile phone.
The 38-year-old also told two primary school-age youngsters “you had to kill” anyone who insulted Islam, Nottingham Crown Court heard.
Ghumra, who had claimed the two boys were making “a false allegation”, will be sentenced on Friday.
Stood emotionless as the verdict was read out after two hours of deliberation by the jury, he was convicted of disseminating “terrorist propaganda” in the form of a graphic Twitter video on his mobile phone, between January 2013 and September 2014.
Prosecutor Simon Davis said Ghumra believed in a “very, very, very extreme” form of Islam.
The court heard how Ghumra, of Haringworth Road, had been working as a pharmacist in Oundle, Northamptonshire and told a customer that members of the so-called Islamic State were “not bad people, they’re only defending themselves”.
The jury was told of how he “brainwashed” the two children, instructing them to not have non-Muslim friends and asking if they wanted to join the terrorist group or help recruit others.
The older boy described being shown “horrible and disgusting” beheading videos asking Ghumra “how can you behead people?”.
He said Ghumra replied: “If you truly believe in Allah, you can do it.”
“He put us on Twitter. He told us to follow whoever he followed. He was following ISIS and really bad people,” said the younger boy in a police interview which was played to the court.
The boy also said that Ghumra made them “business cards” – which were shown to the court – with their names and email addresses on them next to a picture of a rifle.
He taught children about jihad in a rented house and the boys were not allowed non-Muslim friends, the jury heard.
The boy told of how Ghumra asked him to choose between going to Iraq or Syria, or staying in the UK and “manipulating” other people into supporting ISIS.
Following Ghumra’s arrest in September 2015 at Birmingham Airport, a computer was seized showing 1,600 search results for terms including “survival knives” and “bushcraft”.
But neither the phone containing the beheading video or the video itself were recovered when police searched his home.
Sue Hemming, from the Crown Prosecution Service, said, “Zameer Ghumra tried to brainwash impressionable children with this violent ideology by making one watch beheading videos and urging them both to adopt a hard-line religious outlook.
“The children were brave to give evidence and we would like to thank them for helping to secure this conviction of a dangerous man.”
