Damages will be determined later, according to the report.
The tajeover deal was worth $US44 billion ($A62 billion).
Lawyers for Musk and the shareholders were not immediately available for comment.
The verdict on Friday from a jury in San Francisco federal court came in a closely watched trial where Musk, the world's richest person, was accused of falsely claiming that Twitter under-reported how many fake and spam accounts, known as bots, were on its platform.
Musk ultimately completed his purchase of Twitter in October 2022 and renamed it X. He has since folded it into his rocket and space exploration company SpaceX.
The civil trial began on March 2, and jurors began deliberating on Tuesday.
Musk has often chosen to battle shareholders in court rather than settle. This included a 2023 trial in San Francisco over whether he defrauded Tesla shareholders who claimed to suffer losses after he falsely claimed in 2018 to have "funding secured" to take the electric car company private, and litigation in Delaware over his $US139 billion ($A197 billion) Tesla pay package. Musk won both cases.
In the latest trial, Twitter shareholders challenged Musk for having publicly questioned on three occasions after agreeing in April 2022 to buy Twitter whether the company was overrun with bots, and perhaps had 20 per cent or more rather than the five per cent it disclosed.
Shareholders cited, among other things, a May 17, 2022, tweet where Musk said his takeover "cannot go forward" until Twitter's chief executive proved the bot percentage was less than five per cent.
"He trashed the company. Trashed the executives. And tanked the stock," the shareholders' lawyer, Mark Molumphy, said during his closing argument on Tuesday.
Michael Lifrak, a lawyer for Musk, countered that the billionaire's concern about bots was real, and that speaking out about the problem did not show Musk committed or intended to commit fraud.
The lawsuit covers investors who claimed to sell Twitter shares at prices Musk artificially depressed between May 13 and October 4, 2022.
Musk is separately in talks to settle a US Securities and Exchange Commission civil lawsuit accusing him of waiting too long in 2022 to disclose his initial purchases of Twitter so he could buy more at low prices before investors saw what he was doing. SpaceX bought Musk's artificial intelligence company xAI, which housed X, in February.
The purchase created the world's most valuable private company, worth about $US1.25 trillion ($A1.77 trillion) at the time.
