More than 100 people packed into Courtroom C, including dozens of photographers and videographers.
The celebrated runner began sobbing, covering his face with his hands, as the charge against him was read out.
Chief magistrate Desmond Nair told him: 'Take it easy. Come take a seat.'
The hearing came after a two-hour delay while Pistorius's lawyers objected to the scrum of local and international reporters packed into the courtroom.
Trish Taylor, mother of Pistorius' ex-girlfriend Samantha Taylor, wrote on Facebook: 'I'm so glad Sammy is safe and out of the clutches of that man.'
But another ex-girlfriend, Jenna Edkins, defended Pistorius in messages Friday on Twitter.
'All I am saying is let him speak, let his side be heard without jumping to conclusions,' Edkins wrote.
She offered 'love and support' to the Pistorius family and wrote: 'I have dated Oscar on and off for 5 YEARS, NOT ONCE has he EVER lifted a finger to me or made me fear for my life.'
Meanwhile, police said today that an autopsy on the body of the victim was taking place. Lt Col Katlego Mogale said the results of the autopsy would not be published.
The court opened at just before 7am GMT today, as he arrived.
Pistorius had initially been expected to appear in court yesterday, but the hearing was postponed to allow forensics more time to study his mansion.
As he awaited his hearing, the Afrikaans-language Beeld newspaper claimed Miss Steenkamp had been shot four times, in the head, chest, pelvis and hand through the bathroom door.
Dressed in a grey hooded jacket, tracksuit trousers and trainers, Pistorius, 26, walked with head bowed from the Boschkop police station yesterday before being taken to Pretoria's Mamelodi Day Hospital in a police convoy.
Brig Beukes said the medical examination was 'standard procedure'.
Pistorius's spokesman, from the Fast Track agency in London, said he was 'assisting the police with their investigations' but no further comment could be made until matters became clearer.
Initial rumours suggested the shooting may have been a Valentine's Day surprise gone wrong.
The couple had only been going out since November.
Miss Steenkamp, a model and law graduate, tweeted the day before Valentine's Day: 'What do you have up your sleeve for your love tomorrow??? £getexcited £ValentinesDay.'
Pistorius appeared to have serious concerns about his safety and was said to sleep with a revolver by his side.