The BBC Radio 1 DJ counted down the entire chart at the end of his Chart Update show, only to realise later that it was actually the chart from four weeks ago.
The chart rundown included Leona Lewis landing at three with 'Trouble', despite having already played The Wanted's 'I Found You' at three just moments before.
After the news, James confessed to the listeners and Chart Show host Reggie Yates that the wrong chart had been played.
He said: "Lots of things are going wrong today. I've got a confession to make. The rundown which we did about five mins ago was in fact a rundown from four weeks ago.
"The wrong one went out on air. Genuinely it was a mistake. What we should do to appease the Official Charts Company and all of the chart fans is to do the real countdown."
The presenter then proceeded to count down the official chart, which placed Robbie Williams at number one for a second week with 'Candy'.
Greg James's Radio 1 colleague Nick Grimshaw has been criticised for stating that Williams has become "irrelevant" on the station, and that he has never heard a track by the singer.