The hearing started in private in the city of Tianjin on May 22, state media said, even though it had been supposed to be an open trial. No explanation was given for the change, but it will raise suspicions that the party either wanted to play down the extent of corruption at the highest levels or that some darker secret was being suppressed.
State television showed Zhou pleading guilty to all charges. "I've realised the harm I've caused to the party and the people. I plead guilty and I regret my crimes," he was filmed saying. "I accept the court verdict, and I will not appeal."
President Xi Jinping has launched a campaign against corruption at every level of the Communist Party, pledging to pursue the "tigers" at the top as well as the "flies" at the bottom.
Few in China doubt that Zhou, who rose through the notoriously corrupt state oil industry, had acquired huge wealth for himself, his family and friends.
Xinhua, the official Chinese news agency, reported he had been convicted of taking bribes worth 133 million yuan ($30.6 million). He had abused his power to allow others to make 2.2 billion yuan from various business dealings. The court found that Zhou had "inflicted enormous damage to public finances and the interests of the nation and the people".
Total estimates of his wealth have run to the hundreds of millions of dollars.
But few also doubt that politics lay behind his downfall. As a member of the Standing Committee, Zhou was one of nine men on the most important body in the country.
He was a close ally of Bo Xilai, a fellow Politburo member who openly opposed the former leadership of president Hu Jintao and Prime Minister Wen Jiabao.
Bo fell from power amid extraordinary circumstances: his wife was convicted of the murder of a British businessman, Neil Heywood, and he was accused of corruption.
During the transition to the leadership of Xi, there were rumours of plots and even attempted coups involving Zhou and Bo. After Bo was convicted, Zhou's downfall began. He was officially placed under investigation for alleged corruption in late 2013.
There were rumours that a death sentence was being prepared, to scare off future challengers and the ultra-corrupt. In the event, he was spared the capital penalty and, save for his guilty plea, his trial was a closed affair. Telegraph Group Ltd