Police said Yeshshiembet Girma, 28, and Muluemebet Girma, 21, of London, would appear at the capital's Bow Street Magistrates' Court on Friday charged under the Terrorism Act 2000.
They were arrested on 27 July in a raid on a public housing estate in the Stockwell area of south London.
Police accused them of failing to give information to detectives which could help convict someone "for an offence involving the commission, preparation or instigation of an act of terrorism".
The failed bombings on 21 July came two weeks after four bombers killed 52 people and themselves in three underground trains and a bus. Police have linked the bombers to al-Qaida.
Thousands of police took to the streets on Thursday to reassure jittery Londoners as al-Qaida's second in command appeared on a video broadcast warning of further attacks.
The charge against the sisters is similar to the one filed against Ismael Abdurahman, 23, the first to be accused in Britain in connection with the failed attempt to repeat the 7 July bombings in London.
Abdurahman appeared in court for the first time earlier on Thursday, where he was remanded in custody for another week. He entered no plea, but his lawyer said he denied any connections to terrorism.