The trip came after Nato secretary-general Anders Fogh Rasmussen said the Libyan leader’s “reign of terror” was coming to an end.
Meanwhile, eight Libyan army officers, including five generals, were paraded in Rome at an Italian Government-arranged news conference.
They claimed to be among 120 military officials and soldiers who have defected in recent days.
Libya’s UN ambassador, Abdurrahman Shalgam, who has also defected from the regime, said all 120 of the military personnel were outside Libya now but he did not reveal their whereabouts.
Libyan state TV pictures showed Gaddafi greeting Mr Zuma and other officials and then walking with them down a corridor.
Gaddafi and Mr Zuma’s delegation were then seen sitting in white armchairs in a large room. The broadcast did not say where the meeting took place.
Gaddafi had not been seen in public since May 11, when Libyan state television showed him meeting what it said were tribal leaders.
On arrival at the airport, Mr Zuma was met by a band and children chanting “we want Gaddafi” in English, while waving Libyan flags and pictures of the leader.
The visit is Mr Zuma’s second since the conflict began in Libya in February. His previous trip made little progress because Gaddafi has refused to relinquish power, while rebel leaders say that is a pre- condition for any truce.
Nato warplanes have been intensifying their airstrikes on Tripoli, with Gaddafi’s Bab al-Aziziya compound in the centre of the city being hit repeatedly.
Journalists escorted into Bab Al-Aziziya after Mr Zuma’s arrival found a group of around 160 African visitors chanting pro-Gaddafi slogans and waving flags of nations including Chad, Niger and Ghana, in an apparent show of pan-African unity.
Britain said on Sunday it was to add “bunker-busting” bombs to the arsenal its warplanes are using over Libya, a weapon it said would send a message to Gaddafi that it was time to stand down.
Mr Rasmussen told a Nato forum in Varna, Bulgaria: “Our operation in Libya is achieving its objectives ... we have seriously degraded Gaddafi’s ability to kill his own people.
“Gaddafi’s reign of terror is coming to an end. He is increasingly isolated at home and abroad. Even those closest to him are departing, defecting or deserting.”
Gaddafi has denied attacking civilians, saying his forces were obliged to act to contain armed criminal gangs and al Qaeda militants.
He says the Nato intervention is an act of colonial aggression aimed at grabbing Libya’s plentiful oil reserves.
Britain and other Nato powers are ratcheting up military intervention in an attempt to break the deadlock in the country as Gaddafi hangs on to power despite a rebel uprising against his four-decade rule and weeks of airstrikes.
US Admiral Samuel Locklear, commander of the joint operations command based at Naples in Italy, declined to comment on whether Nato would put forces on the ground.
However, he suggested a small force might be needed to help the rebels once Gaddafi’s rule collapses.
He said: “I would anticipate there might be a need at some point to unfold a small force ... a small number of people there to help them in some way.”