The 77-year-old spent a week in Aleppo, where he came under sniper fire as he tried to take pictures of the conflict.
McCullin told BBC Radio 4's Front Row he "hadn't seen any real evidence of what's been going on" in Syria, so he decided to take one final assignment.
His aim, he added, was to show the human toll of the fighting.
"We don't need any more scenes of snipers and rebels firing over brick walls," he told the BBC. "What we really need is the human interest side of this story."
McCullin in final front-line trip
War photographer Don McCullin tells the BBC why he came out of retirement to document the conflict in Syria.
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