Hashem Abedi appeared at Oxford Crown Court on Monday via video-link from Belmarsh Prison in southeast London.
Judge Nigel Sweeney ordered the 22-year-old to be placed in custody before a preliminary court hearing at the Old Bailey in London or in Oxford on July 30.
Abedi travelled to Libya before his older brother detonated his suicide vest on May 22, 2017. He is suspected of helping plan the attack.
He faces almost two dozen counts of murder for the attack's victims, one count of attempted murder for those injured and one count of conspiring with his brother to cause explosions.
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