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.

Steven Van de Velde, 21, admitted three counts of rape against a child he met after travelling from Amsterdam in August 2014.
The girl was raped near Furzton Lake and at an address in Milton Keynes.
Van de Velde returned to the Netherlands, but was extradited and arrested in January.
He appeared at Aylesbury Crown Court via a video link for sentencing after admitting all three offences last month.
The court heard he was aware of the girl's age, having had conversations on various social networking sites.
He went to the girl's home when her mother was out and had sex with her, taking her virginity.
Sentencing him, Judge Francis Sheridan said: "You were a potential Olympian. You had the possibility of a stellar future representing the Netherlands.
"She was a child aged 12. You were fully aware of that fact."
Van de Velde - of Cornelis De Wittlaan, Den Haag - travelled from Amsterdam on 2 August 2014, having booked a return ticket with EasyJet that day.
Prosecutor Sandra Beck said: "She had got very close to him via Facebook and spoke regularly. He made her feel very special.
"He is a member of the national volleyball team and she liked what she saw."
Mitigating, Linda Strudwick said: "There is genuine remorse. He has lost a stellar sports career and has been branded a rapist. Plainly it is a career end for him. "
Two men have been convicted of killing a stranger by throwing him over a bridge into a canal.
[NEXT_CONCEPT]
A Dutch international volleyball player who raped a 12-year-old British girl he met on Facebook has been jailed for four years.