A military prosecutor charged Talaat Sadat, who also is an opposition lawmaker, with "spreading false rumours and insulting the [Egyptian] armed forces" after questioning him for six hours, officials said on Sunday.
In an interview with the private, Saudi-owned Orbit TV station last week, Talaat Sadat alleged that the assassination was an "international conspiracy" with the participation of his uncle's personal guards and some army commanders.
He claimed both the US and Israel were involved.
Anwar Sadat, the former Egyptian president, was killed during a military parade in Cairo on October 6, 1981.
Sadat also questioned the promotion of some of the guards by the government of Hosni Mubarak, the Egyptian president, who replaced Sadat.
Talaat Sadat's trial is scheduled to begin on October 11, they said. He could face a five-year prison term if found guilty.
Sadat has denied the charges, saying the Egyptian government wants to "get rid" of him because he expresses opposition.
No legal concerns
Earlier in the week, Talaat Sadat told the Arabic independent daily, Al Masry Al Youm, he would ask the parliament to form a committee to reinvestigate the circumstances of his uncle's assassination. If the parliament did not agree, he said he would go to the UN.
Following those remarks, Fathi Sorour, Egypt's parliament speaker, stripped Talaat Sadat of his parliamentary immunity - a step necessary to bring any charges against him.
Anwar Sadat's family members have distanced themselves from the former president's nephew, saying Talaat Sadat speaks for himself.
"From a legal point of view, I'm not concerned," Talaat Sadat said on Sunday. "But I'm worried about a vindictive regime, which knows nothing about democracy or respecting lawmakers or citizens."
An Egyptian group also has asked the UN to investigate Sadat's death similar to the UN's effort to look into last year's assassination of former Lebanese prime minister Rafiq Hariri.
The group, The Free Egyptians, has collected about 9,270 signatures in an internet petition to Kofi Annan, UN secretary-general.