Fr Samaan Shehta, 40, died in hospital after he was struck on the head with a cleaver in a poor district of Cairo.
The Cairo Criminal Court said the culprit, Ahmed Saeed, was responsible for the cleric's death and for wounding another priest.
The attack was one of several deadly assaults last year on Egypt's Christian minority, which account for ten per cent of the country's population.
A spate of suicide bombings claimed by IS in the predominately Muslim nation has killed more than 100 people since December last year.
The court's verdict can be appealed.
Egypt ranks number 17 on the Open Doors World Watch List of the most dangerous countries to be a Christian in.
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