The double-amputee sprinter, who is on trial for murder, was questioned by prosecutors over why Reeva Steenkamp had failed to scream when he shot her four times through a toilet door.
Gerrie Nel, one of South Africa's top attorneys, said it was beyond belief Ms Steenkamp would have remained silent in the cubicle with an armed Pistorius shouting and screaming in the adjoining bathroom.
The prosecution alleges the 29-year-old model took refuge in the toilet during an angry row with the athlete, and he then shot her through the door.
Pistorius, who says he fired at what he thought was an intruder, has testified Ms Steenkamp did not cry out during the incident in the early hours of February 14, 2013.
However, under cross-examination from Mr Nel - known in South Africa as "The Pitbull" - the 27-year-old runner, who denies murder, was forced to concede he could not have heard whether she screamed or not because his ears were ringing from the sound of gunfire.
People living nearby have testified to hearing a woman's terrified screams before and during a volley of shots.
"She's awake. She's in the toilet. You're shouting. You're screaming. You're three metres from her. She would have responded. She would not have been quiet, Mr Pistorius," Mr Nel said.
"She didn't respond, my Lady," an apparently distressed Pistorius replied, addressing judge Thokozile Masipa.
"Did she scream at all whilst you shot her four times?" Mr Nel continued.
"No, my Lady."
"Are you sure? Are you sure, Mr Pistorius, that Reeva did not scream after the first shot?" Mr Nel continued. "Are you, Mr Pistorius?"
After a brief silence, Pistorius said: "My Lady, I wish she had let me know she was there."
Questioned further on the matter, he said: "I don't think I would have heard her," to which Mr Nel replied: "Exactly."
"A gunshot went off. My ears were ringing," Pistorius said.
"How can you exclude the fact she was screaming if you couldn't hear?" Mr Nel asked.
Pistorius then conceded: "My Lady, the sound of that gunshot in the bathroom, you wouldn't have heard anyone scream. The decibels of the gunshot, I don't believe you would have heard anyone scream. When I had finished firing the gunshots, I was screaming and I couldn't hear my own voice."
Mr Nel followed up with his central accusation - that the couple had an argument and Ms Steenkamp fled to the toilet pursued by Pistorius, who shot her through the locked door.
Ms Steenkamp was hit by three of the four rounds Pistorius fired. A police ballistics expert has testified that the first round hit her hip and the final one her head, killing her almost instantly.
"You knew that Reeva went behind the door and you shot at her," Mr Nel said.
"You shot at her knowing she was behind the door."
Pistorius, who faces life in prison if convicted of murder, denied this, before the court adjourned until Monday.
The trial has gripped South Africa and millions of sports fans around the world who have seen Pistorius as a symbol of triumph over physical adversity.
His lower legs were amputated when he was a baby but, running on carbon fibre prosthetic limbs, he went on to achieve global fame as the "fastest man on no legs", winning numerous Paralympic gold medals and reaching the semi-finals of the 400 metres in the 2012 London Olympics against non-disabled athletes.