The jury returned a unanimous verdict of guilty after considering their verdict for more than seven hours.
The trial has captured national attention in recent weeks.
Mr Justice Hunt had asked that there be silence in court before the verdict was read out. This was observed impeccably by the public.
Mr Justice Hunt told the jury that their behavior was an example of “first class good citizenship” following the case.
He also said he “110 per cent” agreed with their verdict “based on the evidence”.
April 20th has been set for a sentence hearing pending the preparation of victim impact statements. The offence of murder carries a mandatory life sentence.
Mr Dwyer (42), an architect from Kerrymount Close in Foxrock, was charged with murdering childcare worker Ms O’Hara (36) on August 22nd, 2012.
Her remains were found in forestry on Killakee Mountain, Rathfarnham, Dublin, on September 13th, 2013. He had pleaded not guilty.
The trial lasted for nine weeks and focused on the sadomasochistic relationship between Mr Dwyer and Ms O’Hara.
During his summation Mr Justice Hunt told the jury if there had been a reasonable possibility Elaine O’Hara died by suicide, Mr Dwyer must be acquitted.
He had told the jury they had to be satisfied beyond reasonable doubt that Mr Dwyer murdered Ms O’Hara by stabbing her for his own sexual gratification.
“You cannot convict unless you are satisfied beyond reasonable doubt; if you are so satisfied, you are obliged to convict,” he said.