Mohamed Sayed Saber Ali, 35, was accused of taking documents from Inshas, one of Egypt's research nuclear reactors, and passing them to foreign contacts - an Irish and Japanese national - for $17,000.
The court said the activities of Ali, also an employee at the state Atomic Energy Agency, between February 2006 and February 2007 "damaged the country's national interests."
Two foreign contacts, identified as Brian Peter and Shiro Izo, were tried in absentia and received similar sentences.
Ali was arrested in February when he arrived from Hong Kong, one of several foreign trips, where he met with Peter and Izo, Egyptian media reported earlier.
Ali pleaded not guilty to the charge. He said he had informed an Egyptian diplomat in Saudi Arabia that the foreigners had said they wanted him to work for their company from within the Atomic Energy Agency.
But the diplomat, Ahmed Bahaa Eddin, told the court he thought the defendant had contacted him because he was worried his spying for Israel might come to light and he had handed classified information over to the foreigners.
Israel has denied the allegations that it recruited the engineer to provide information on Egypt's nuclear activities.
This is the second case of espionage involving Israel in Egypt this year. Another man with dual Egyptian-Canadian citizenship was sentenced to 15 years in prison and fined about $1,500 for spying for the Jewish state. Investigators said the man had gathered information on Arabs living in Turkey and Canada for Israel's Mossad.
Last year, Egypt said it was resuming its civilian nuclear energy program and was planning to build its first three nuclear power plants of 600 megawatts each.
Reactors in Egypt, a signatory to the Nuclear Non-Proliferation Treaty, are under United Nations supervision.
