Kardashian arrived in court in a black van on Tuesday, accompanied by her mother.
Cameras are not allowed in the courtroom, and her testimony will not be broadcast live.
The billionaire celebrity was robbed at gunpoint in her hotel room in 2016, an attack which stylist Simone Harouche told the court had been traumatising.
The suspects are accused of tying up Kardashian with zip ties and duct tape before making off with jewels worth millions of dollars, including a $US4 million ($A6.2 million) engagement ring given to her by her then-husband rapper Kanye West (now known as Ye), according to investigators.
Before Kardashian's testimony, Harouche, who was asleep in the same luxury hotel flat at the time of the attack, spoke to the court on Tuesday morning.
"'I have babies, and I have to live' - that's what I heard her say.
'Take everything - I need to live'" said Harouche, who was downstairs in the duplex flat at the time of the attack, while Kardashian was upstairs.
"We've been friends since we were little girls. So when I heard this sound, it was very different, and it woke me up, because it was a sound that I had never heard from Kim. It was terror," Harouche said.
She rushed to lock herself in the bathroom and texted Kardashian's sister Kourtney and their bodyguard for help.
When the robbers left and Kardashian joined her downstairs, "she was beside herself, I've never seen her like that before," Harouche said.
"She just was screaming and kept saying we need to get out of here, we need help, what are we going to do if they come back."
Yunice Abbas, 71, who is among the 10 suspects standing trial, many in their late 60s or 70s and dubbed "the grandpa gang," has told French media that he and others who took part in the robbery did not know who Kardashian was.
"It's not her, it's her diamond we targeted," Abbas told C8 TV a few years ago. Abbas has admitted his participation in the robbery - and wrote a book about his role.
His lawyer Gabriel Dumenil said that Abbas would apologise to Kardashian if the presiding judge gives him the opportunity to speak on Tuesday "even simply just to say, 'I'm sorry'."
Frank Berton, a lawyer representing 68-year-old Aomar Ait Khedache, nicknamed "Omar the Old," said in April that he hoped the fact that Kardashian was a global celebrity would not affect the trial.
Khedache is accused of being the gang's ringleader, which he denies.
In all, nine men and one woman are being tried by the criminal court.
Five of them - all men - face armed robbery and kidnapping charges and potentially risk being sentenced to life imprisonment, while the others are charged with complicity in the heist or the unauthorised possession of a weapon.
As the robbers escaped on foot or with bicycles, they lost some of the jewellery, including a cross with six diamonds, which a passerby found in the street and brought to the police.
But most of the jewels, including the $US4 million engagement ring, were never found.
