Teenage sensation Mahlambi will remain at the club at least until June 2021, while Hlatshwayo has signed a two-year deal which will expire in June 2019.
The two players have contributed immensely to the Students over the past few years, and they continue to be important members of the current squad.
Wits CEO Jose Ferreira praised Mahlambi's loyalty to the club, and he hopes the attacker will only leave the Students for Europe.
"Phakamani is one of the most talented players in the long and proud history of this club. He personifies our strong and firm commitment to the development of young players and to provide them with the opportunities to play at the highest level, both locally and at international level. By committing his long term future to Bidvest Wits, Phakamani has demonstrated his loyalty to our club and we have no doubt that, with us, he will be able to fulfill his dream of playing overseas," Ferreira told the club's website.
Meanwhile, Mahlambi said while his ultimate dream to play in Europe, he will continue to give his alll and help the Clever Boys win more trophies.
"I'm delighted to have extended my contract at Bidvest Wits and would like to thank them for giving me the opportunity to play professional football in the PSL. The club took good care of me when I was injured and I hope to repay them by helping my team win many trophies. My ultimate dream is to play in Europe and I'm sure that through Bidvest Wits I will be able to achieve both goals," the speedy attacker said.
Speaking of Hlatshwayo, Ferreira said he has no doubt the tough-tackling defender will become one of the legends of South African football.
"I am delighted that Tyson has committed his immediate future to the club. As club captain, Tyson has all the credentials and qualities that all our young players aspire to. I have no doubt that he will become another legend of South African football," said Ferreira.
Hlatshwayo thanked the club for continuing to believe in him and rewarding him with the new contract. He feels he's grown as a player since working with Gavin Hunt.
"I'm very proud and happy to have extended my stay with Bidvest Wits. I feel very privileged with the faith they have showed in me and I believe we will grow together from strength to strength. I have grown as a player at this club under coach Gavin Hunt and I am looking forward to a successful future with my club," said the Wits skipper.