A jury found Michael Bassaly, 31, guilty of first-degree murder after deliberating for less than two hours.
Mr Bassaly fatally shot his mother, Yvonne Zaky Bassaly, in the head in the back of his vehicle outside St Mark Coptic Orthodox Church on 29 August 2013.
Mr Bassaly went on to make a 911 call himself, telling the operator several times that he had shot his 61-year-old mother.
When police arrived at the scene, they found Mrs Bassaly gasping for air with a wound to her head.
She died hours later in hospital.
St Mark Coptic Orthodox Church of Chicago
In court, Mr Bassaly told the jury that he had accidentally shot his mother in an attempt to stop her committing suicide.
But prosecutors argued that his statement contradicted a note found by investigators in his car.
The note, apparently written by Mr Bassaly, was a suicide letter in which he said he had no choice but to kill himself and his mother to avoid a fraud investigation.
It appears that after shooting his mother, Mr Bassaly could not go through with killing himself.
"Michael Bassaly unsuccessfully tried to convince a jury that his mother took her own life," state attorney Robert Berlin said in a statement.
"Today, a jury saw through his lies and feeble attempts to avoid responsibility for the murder of his own mother by claims of suicide.
"This was a very difficult case as the victim and defendant are mother and son. To the entire Bassaly family, I wish them some measure of closure as they come to the final stages of this horrible family tragedy."
Mr Bassaly will be sentenced in court on 22 March. He will face a minimum of 45 years behind bars.