The verdicts bring to five the number of people convicted in London for being part of a global financial conspiracy that has forced banks to pay fines of $9bn (€8bn), discredited rates like Libor and helped shred public faith in the banking industry.
Calcutta-born, US-based Jay Merchant, 45, the most senior of the men on trial, was convicted unanimously.
British former Libor submitter Jonathan Mathew, 35, and former trader Alex Pabon, a 38-year-old American, were found guilty by a majority verdict after a 10-week trial.
A second Libor submitter, 61-year-old Peter Johnson, had pleaded guilty in October 2014.
The four men are expected to be sentenced at London’s Southwark Crown Court later this week.
Reporting restrictions on the verdicts were lifted yesterday after the jury failed to reach a verdict on two other defendants, Greek-born Stylianos Contogoulas, 44, and American Ryan Reich, 34.
The SFO now has 14 days to decide whether it will seek a fresh trial for the two.
The verdicts come four years after Barclays became the first of 11 powerful banks and brokerages to be handed a hefty fine over rate fixing allegations, sparking a political and public backlash that forced out charismatic former CEO Bob Diamond, an overhaul of Libor rules and the criminal inquiry.
The verdict represented a victory for the SFO, which has had a mixed record on successfully prosecuting white collar criminals, and whose head David Green has staked his reputation on the costly and high-profile Libor prosecutions.
The SFO secured its first Libor conviction when Tom Hayes, a former UBS and Citigroup trader, became the first man found guilty by a jury for his role in the Libor scandal last August.
He is serving an 11-year jail sentence after his original 14-year sentence was reduced on appeal.
But the agency suffered a blow when prosecutors failed to persuade a jury six former brokers conspired with him to rig Libor. They were all cleared in January.
The men told the court their bosses sanctioned communications on Libor rates, that they sent emailed Libor requests over corporate message systems in full view of compliance staff, and that such rates commonly reflected banks’ derivatives positions at the time.