Manning, 25, who is charged with leaking more than 700,000 classified files, combat videos and State Department cables to WikiLeaks, told Judge Colonel Denise Lind that he did not want to testify on his own behalf.
"The defense rests, your honor," Manning's lawyer David Coombs told the court after three days of defense testimony.
Manning, who is charged with passing secrets to WikiLeaks while serving as an intelligence analyst in Iraq in 2009 and 2010, could face life in prison if convicted of the most serious of 21 charges, aiding the enemy.
Defense lawyers had read a statement into the record and elicited testimony from nine witnesses. They had originally said they planned to call 46 witnesses.
Lind, who is both overseeing the case and will hand down a decision, has not set a date to announce a decision.
In his opening statement, Coombs sought to portray Manning as naive but well-intentioned in seeking to show Americans the reality of the wars in Afghanistan.
He also tried to downplay the importance of the material Manning is alleged to have leaked or stolen. Defense witnesses testified that much of the material was available on public records before WikiLeaks released it.
The prosecution rested last week after five weeks of testimony, some in closed session, and had about 80 live witnesses or statements read into the record.
Prosecutors alleged that the material supplied to WikiLeaks ended up in the hands of the extremist group al Qaeda.
The defense's final witness, Harvard Law School professor Yochai Benkler, testified that WikiLeaks and its model of decentralized leaking of secrets was a high point in journalism history.
WikiLeaks is "a clear distinct component of what in the history of journalism we see as high points, where journalists are able to come in and say, 'Here's a system operating in a way that is obscure to the public and now we're able to shine the light,'" said Benkler, the co-director of the Berkman Center for Internet and Society.
WikiLeaks provided the materials in 2010 to traditional news outlets that included The New York Times, Britain's Guardian and Germany's Der Spiegel. The publications were able to vet the material and provide greater distribution for it, Benkler said.
The 21 charges against Manning include espionage, computer fraud and, most seriously, aiding the enemy by disclosing material that could be used by the al Qaeda network.
Lind set Monday for a hearing on whether a prosecution rebuttal hearing should be held. She also will rule on defense motions that four of the charges should be dismissed. Such motions are routine in court martials.
If Lind rules that the rebuttal hearing should be held, it will be heard on July 18. If not, closing arguments will be on Tuesday.