Garda Daniel Hickey of Waterford Garda Station was found guilty after a four-week trial of assaulting Anthony Holness, causing him harm, while Garda John Burke was found guilty of perverting the course of justice.
The guilty verdicts are the first to be secured in a jury trial by the Garda Siochána Ombudsman Commission since that body came into being.
Meanwhile, Sergeant Alan Kissane was found not guilty by a jury of assaulting Anthony Holness, causing him harm.
The jury at Waterford Circuit Court has not yet reached a verdict in the case of a fourth defendant — Sergeant Martha McEnery — who is also accused of assault causing harm.
They will resume deliberations in that matter on Monday.
All four gardaí — based at Waterford garda station in Ballybricken in the city — had denied all charges against them.
The incidents at the centre of the trial occurred at about 3am on January 29, 2010, when Anthony Holness was on his way home from a night out. He was seen urinating on the side of the street and, when Garda Hickey decided to arrest Mr Holness, the latter resisted and was then pepper-sprayed, grabbed in a headlock by Garda Hickey, bundled to the ground and punched several times in the back of the head, the prosecution said.
Garda Burke was operating the city’s CCTV system in the communications room at Waterford garda station at the time and was accused of twice directing a camera away from the incident for a number of seconds.