This is the third police killing in the city since Sunday.
Lieutenant Colonel Tembinkosi Kinana said two unidentified men knocked on the sergeant's door at his Montclaire home around 21:00 on Monday.
They fired several shots at him as he approached the door and then entered the house, demanding his firearm in a safe.
They ran away and the officer died at the scene.
The 34-year-old officer had been stationed at Philippi East.
‘An attack on society’
A case of armed robbery and murder was being investigated and no arrests had been made.
"The SA Police Service Management would like to convey heartfelt condolences to the bereaved family of the deceased police officer and to his colleagues," Kinana said.
"An attack to the police, is an attack to the society. Our efforts to serve and protect our communities will not be deterred by the cold blooded and heartless criminals.
"We will not be side-tracked by the criminal elements operating within our communities, and the police will not sleep until culprits are brought to book."
Two policemen were shot dead in separate incidents in Cape Town on Sunday.
A 36-year-old constable was killed while on duty in Spine Road, Mitchells Plain, around 8pm on Sunday.
An hour later, a 40-year-old sergeant was shot in his Khayelitsha home while getting ready to go to work.
He died on his way to hospital.
No arrests had been made for either attack.
Highest incidence of cop killing in Western Cape
Police Minister Nathi Mthethwa visited Mitchells Plain on Monday following the attacks.
In a phone interview, he said the province had the highest number of attacks on police.
He said the Western Cape community safety department's criticism of the police service reinforced the idea that officers did not deserve respect.
"What we are saying is that criticising the police is not a problem if they think there are weaknesses. But if they say nothing positive, they open them [the police] up to criminal attack," he said.
"The major point we're making here is the issues of safety and security, like in any other province, is about working together and partnerships through a multi-disciplinary approach," he said.
Community safety MEC Dan Plato condemned the police minister's comments, accusing him of "playing politics" while people were being killed.
"It is utterly disgusting and totally inappropriate that the national minister would use the death of police officers for electioneering purposes," Plato said.
Mthethwa urged to retract comments
The Democratic Alliance (DA) accused Mthethwa on Monday of trying to score political points, calling his comments distasteful, insensitive and an insult to the grieving families.
"The only people to blame for the deaths of our police officers are criminals who have no respect for the police," DA MP Dianne Kohler-Barnard said.
She called on Mthethwa to retract his comments.
"[He must] stop abusing his position to make irresponsible statements. Instead, he should be proactive and launch an investigation into the causes and extent of police killings," Kohler-Barnard said.
The DA intended asking Parliament to summon Mthethwa to explain what he would do to better protect police officers in the Western Cape and the rest of the country.