Fars News Agency said the death sentence for Saeed Malekpour was upheld by the Supreme Court, confirming reports earlier this month.
Judges had annulled the death sentence in June, which was handed down for alleged antigovernment activities and developing adult Internet content.
No explanation has been given as to why the court reversed itself.
Malekpour's supporters say he developed a program that allows photographs to be posted to the Internet that was used without his knowledge for the creation of pornographic websites.
A resident of Canada since 2004, Malekpour was arrested in Iran in 2008 while visiting his dying father.
Reporters Without Borders expressed "shock" over the original verdict.
Canadian Foreign Minister John Baird on January 17 condemned the Iranian court's reported decision to reinstate the sentence.
Family members have suggested the judiciary was under pressure from the Islamic Revolutionary Guards Corps to order Malekpour's execution.
Malekpour's sister, Maryam, argued that her brother's computer code could have been used by anyone and was used by adult content publishers without his knowledge.
She has also questioned televised confessions her brother made in 2010 in which he admitted to all of the charges against him, saying he was coerced. Maryam Malekpour says the prosecution's case relied almost solely on those confessions.
A number of Iranians have emerged from prison saying they were tortured into such confessions, which are frequently then broadcast on state television.
Amnesty International says Iranian executions have been on the rise in recent years, with at least 600 people put to death in the 11 months through November.
compiled from agency and RFE/RL reports