The jury also found father and son Greg and Travis McMichael and neighbour William “Roddie” Bryan guilty of attempted kidnapping, and the McMichaels guilty of the use of a firearm in the commission of a violent crime.
The hate crimes trial proceeded after Judge Lisa Wood last month rejected a plea deal that would have allowed the McMichaels to be placed in a federal prison before they were returned to the Georgia prison system, widely perceived as a tougher environment for inmates compared to federal penitentiaries.
A sentencing date for the federal charges has not yet been set.
Wanda Cooper-Jones, Arbery's mother, criticised the Department of Justice for originally agreeing to accept a plea deal.
"They ignored my cry. I begged them. Even after the family stood before the judge ... and asked the judge to not take this plea deal, the lead prosecutor, Tara Lyons, stood up and asked a judge to ignore the family's cry," Ms Cooper-Jones told reporters after the verdict was reached.
"That's not justice for Ahmaud."
Ms Cooper-Jones said Tuesday's verdict would not have happened were it not for the pressure the family put on the department.
"What the DOJ did today, they was made to do today," she said.
Wednesday marks the second anniversary of Arbery's killing.
During the trial, prosecutors showed about two dozen text messages and social media posts in which Travis McMichael and Bryan used racist slurs and made derogatory comments about black people. The FBI wasn’t able to access Greg McMichael’s phone because it was encrypted.
The February 23, 2020, chase ended with Arbery cornered and Travis McMichael firing three shotgun blasts at point-blank range that left Arbery dead at the scene.
Mobile phone video of the incident recorded by Bryan stirred public outrage when it surfaced on social media about two months later, at a time when police had yet to make arrests in the case.
Prosecutors presented jurors with a lengthy history of overtly, sometimes violently, racist slurs and social media commentary by the three men as evidence that the accused had singled out Arbery because of the colour of his skin.
“They were motivated by racial assumption, racial resentment and racial anger,” Christopher Perras, a special litigator for the US Justice Department's civil rights division, said in his summation on Monday.
“They saw a black man in their neighbourhood and they thought the worst of him.”
Defence lawyers focused on Arbery's conduct, arguing the McMichaels chased after him not because he was black but because they had seen him on four previous occasions at night at a house under construction and believed his actions were suspicious.
Bryan's lawyer said his client joined the pursuit in his own vehicle when he saw the McMichaels driving after Arbery yelling at him to stop and assumed the man they were chasing was running away because he had “done something wrong".
The defence did not deny the bigoted social discourse and racial epithets of their clients over the years but insisted those did not prove racist intent for their actions towards Arbery.
Agencies contributed to this report