"Many people adhered to the moral values of Jedi knights from the Star Wars saga," the Czech Statistical Office said, noting that the invented faith also had a strong following in countries such as Australia, New Zealand, Canada and Britain.
It said 15,070 Czechs registered as Jedi knights in the census held in March, against 1,083,899 Roman Catholics and 707,649 people who said they believed in God but did not belong to any church.
"Fifteen thousand adherents, which is the size of a small town, is not a negligible social phenomenon," Stanislav Drapal, deputy head of the statistical office, said.
In Prague, statisticians registered 3977 Jedi knights, or 0.31 per cent of the capital's population.
The lightsabre-wielding Jedi knights are an order of guardians of peace for the interplanetary Galactic Republic of the cult Star Wars series, known for their enhanced mind powers that allow them to harness "The Force" to control objects and influence others.
Their moral code has long struck a chord among fans of the films, some of whom over recent years have decided to live their lives according to the Jedi philosophy, which taps elements of several existing religions.
"We included this option (in the census form) despite a fierce debate over whether it's serious or not. But it's not up to statisticians to say what is or is not a religion," said Mr Drapal.
Almost five million people left the religion column empty.
"If we add the 3.6 million citizens who said they were not religious at all, it looks as if Czech citizens ignored the issue or as if they really had no relationship to faith and religion," Mr Drapal said.