Sometime later that night, prosecutors say, Kercher was killed in what began as a sex game, with Sollecito holding her by the shoulders from behind while Knox touched her with the point of a knife.
Kercher's body was found the next day in a pool of blood in the apartment she shared with Knox in Perugia, central Italy.
Alternating between English and Italian, Knox told the court that she last saw Kercher on the afternoon of Nov. 1. They talked about what they had done the night before - a Halloween night out - and Knox said Kercher still had a bit of her vampire makeup on.
Sollecito then arrived at the apartment and he and Knox had something to eat while Kercher was in her room, Knox told the court.
"She left her room, said 'bye,' walked out the door," Knox said, at this point speaking Italian. "That was the last time I saw her."
She told the court that she and Sollecito had gone to Sollecito's house, where they stayed until the next morning.
"I told Raffaele that I wanted to watch a movie so we went to his place," Knox said. After dinner, they went upstairs to his room, she said.
"I sat on the bed, he sat at his desk, he prepared the joint and then we smoked it together," she said. "First we made love, then we fell asleep."
Knox and Sollecito have been jailed since shortly after the slaying. They are both charged with murder and sexual violence.
They could face Italy's stiffest punishment, life imprisonment, if convicted of murder.
Knox occasionally paused to take a breath and had a blemish on her upper lip, which her family said was a cold sore caused by stress. However, during most of her testimony she appeared calm and confident.
Sollecito, 25, has said he was at his own apartment the entire night of Nov. 1, mainly working at his computer. He said he does not remember if Knox spent the whole night with him or just part of it. The two have said they could not remember events clearly because they had taken drugs.
Knox also repeated accusations that she was beaten by police and confused when she was questioned in the days after the killing. Police have denied any misconduct.
After the killing, Knox accused Diya "Patrick" Lumumba, a Congolese man who owns a pub in Perugia, of being the culprit. Lumumba was jailed briefly in the case, but he is no longer a suspect and is seeking defamation damages from Knox.
Knox was called to testify both in her own defense and in a civil case brought by Lumumba.
"The declarations were taken against my will, so everything that I said was said in confusion and under pressure," Knox said under questioning by Lumumba's lawyer.
"They called me a stupid liar; said I was trying to protect someone. I was not trying to protect anyone," she said. "I didn't know what to respond. They said I left Raffaele's home, which I denied, but they continued to call me 'stupid liar."'
Knox smiled as she walked into the court before her testimony. She was dressed in a white shirt and white trousers and had her hair pulled into a ponytail.
Knox's father, Curt Knox, said his daughter looked "confident in what she wants to say."
"She has nothing to hide," he told The Associated Press during a break. He said he hoped people could now see a "different Amanda," - different from the way she has been portrayed by the media so far.
The trial began in January and a verdict is expected after a summer break.
A third suspect in the case, Ivory Coast national Rudy Hermann Guede, was found guilty of murder and sexual violence and was sentenced to 30 years in prison. He was given a fast-track trial at his request, and his appeal is set to start in November. He, too, denies wrongdoing.
The trial has been closed to cameras but the presiding judge, exceptionally, allowed them in to film for Knox's testimony - only to ask them to leave a few minutes later for causing too much disruption. The cameras were then crammed in the press room, where proceedings were being shown on a screen.