John and Edward Grimes, 19, who found fame on The X Factor, performed their song Lipstick in the run-off.
Israel’s Dana International, who won Eurovision in 1998, failed to make the cut.
Jedward will be among 25 acts in today’s grand final, including Blue, who will sing I Can for the UK.
The pair were dressed in red sparkly jackets with big shoulders for their frenetic performance.
Before the semi-final, the twins said they were not nervous at the prospect of singing before an estimated TV audience of 150 million people.
The act have promised to be “the Pavarotti of Eurovision”.
