"The court finds the accused is fit to stand trial," Judge Kate Pillay said.
Ntshongwana also faces charges of attempted murder, kidnapping and rape.
He allegedly hacked two of his victims to death with an axe. One was decapitated.
Thembelenkosini Cebekhulu was killed in Montclair on March 20, Paulos Hlongwa in Lamontville on March 22, and Simon Ngidi the next day.
The court heard that Ntshongwana was diagnosed at Durban's RK Khan Hospital with schizophrenia and a bipolar condition in December 2009.
In January, psychiatrist Dr Soobian Moodley testified that Ntshongwana had not shown any signs of mental instability during medical assessments.
"Clearly, the alleged crimes were premeditated and deliberate and from my observation he could go on for a long time without relapse," he said at the time.
"Generally, it's very unusual for people with the condition to be aggressive and violent."
On Friday, Pillay said the four psychologists who examined Ntshongwana testified that he was able to understand court proceedings, to communicate coherently, to understand the charges and make a proper defence.
"Mr Toni [defence attorney Herbert Toni] has accepted these findings. There is no dispute about the accused's ability to understand court proceedings," she said.
The matter was postponed for trial on November 19. Ntshongwana remains in custody.