Jay Merchant was convicted unanimously of manipulating the key financial rate between 2005 and 2007.
Jonathan Mathew and Alex Pabon were found guilty by majority verdict after a ten-week trial.
A fourth employee, Peter Johnson, pleaded guilty before the trial began.
Sentencing will take place on Thursday.
This brings the number sentenced for Libor-rigging to five. Hayes was convicted of eight counts of conspiracy to defraud in August 2015 and sentenced to 14 years in prison, later reduced to 11 years on appeal.
In March, Hayes was ordered to pay a confiscation order of £878,806 today at Southwark Crown Court. Mr Justice Cooke, who oversaw the trial and confiscation proceedings, found that Hayes would not have been rated as highly as he was by UBS and Citi if he had not achieved success in the manipulation of Libor and therefore would not have been rewarded as highly.
