Martin Toland, 34, of Walkinstown Park, was found guilty by a majority jury verdict in the Central Criminal Court.
He had denied murdering 28-year-old Alan Nolan at his apartment in Ballyfermot in September 2007 and claimed he acted in self defence.
Mr Nolan received five stab wounds, including the fatal wound that penetrated his heart to a depth of 5cm, and another wound that went clean through his shoulder.
Toland was also found guilty of a second count of recklessly or intentionally causing serious harm to 30-year-old James Carroll during the same incident.
Mr Carroll narrowly survived after Mr Toland stabbed him in the heart and stomach. He went on to give evidence and was the main witness in the trial.
The three men had spent the night in question drinking, taking ecstasy and playing PlayStation games and poker for money.
In the early hours of the morning, a row broke out between the accused and his friend, Mr Nolan, who accused Mr Toland's sister of being responsible for a series of prank calls he had been receiving.
Speaking after the verdict, Mr Nolan's uncle, Gay Nolan, said justice had been done.
'He got everything he deserved,' Mr Nolan said of the accused. 'That's what he gets for telling lies,' he added.
'I'm relieved to stand here today and see justice being done for Alan,' Mr Nolan finished.
Mr Justice Patrick McCarthy handed down the mandatory life sentence.
He adjourned sentencing for the second charge until 22 March, when he said the court will hear victim impact statements from both Mr Nolan's family and from Mr Carroll.
