Mark Munro, 31, and James Robertson, 27, pushed Russell Robertson over railings at Bainsford Bridge, Falkirk, on 29 May last year.
Mr Robertson, 27, suffered a skull fracture caused by his head hitting a metal stanchion as he fell.
The two men, who were accused of murder, were convicted of the lesser charge of culpable homicide.
The High Court in Glasgow heard that Mr Robertson would have been unconscious when he went into the water.
His body was recovered from the canal more than an hour later.
The court heard that all three men had been at the Warehouse nightclub in Falkirk and were making their way home after 03:00 when an incident occurred.
James Robertson was approached by Russell Robertson and they began fighting, before Munro, who had been on the phone, became involved.
The trial heard the men tipped Mr Robertson into the canal and then ran off without a backward glance.
Both accused blamed each other during the trial.
Robertson admitted being in an initial struggle with Russell Robertson, but claimed he was walking away towards Falkirk when he went into the water.
Nightclub security manager Kevin Gibney said he saw Russell Robertson disappear off the bridge as he struggled with Munro and Robertson.
Mr Gibney said: "One minute he was there and the next he was gone. The two gentlemen ran across the road."
Judge Lady Carmichael deferred sentence until 23 August at the High Court in Edinburgh and detained both men in custody.
Two men have been convicted of killing a stranger by throwing him over a bridge into a canal.