A former chaplain at a Perth girls' school has been sentenced to 15 months in jail for possessing child pornography.

Matthew David O'Meara was the chaplain at Perth College in Mt Lawley when hundreds of pornographic images were found on two computer thumb drives belonging to him.

O'Meara denied any knowledge of the material and suggested at his trial that he had been set up.

Despite his claims, a District Court jury found him guilty of all four charges.

At the sentencing hearing on Thursday, the court was told O'Meara, who has two young children, was ruined both professionally and financially.

O'Meara will have to serve seven-and-a-half months in jail, before he can be released on parole.

His wife, Karina O'Meara, insists her husband is innocent and said she will continue to support him.

"We all stand by Matthew, 100 per cent," she said.

"We believe that he has suffered a terrible injustice, a brutal injustice.

"We're going to do what we can to regroup and consider an appeal and we'll do what we can to advance the cause for justice for him as soon as possible.

"We know this is not the actions of Matthew O'Meara and that's all I wish to say about the matter at this point."