Nomvethe, who turns 40 in December, made his first appearance of 2017/18 as a substitute in the 2-0 loss at Chippa United on August 22, having sat out the 1-0 win over Free State Stars on the opening day of the campaign.
'Bhele' - the PSL's record marksman with 119 strikes - netted 17 goals in 27 games last term.
“Well, Siyabonga Nomvethe is a great professional and a role model to many,” Morton told the club's website.
“He has been playing at the highest level for a very long time and there’s a lot that one can learn from him as a teammate.
“He’s done an unbelievable job of taking care of his body – hence he is still active and playing professional football.
“It’s great to have him as a teammate in the team. His experience will be very important to the team this season,” concluded the midfielder, who is on loan at Usuthu from SuperSport United.
Cavin Johnson's side next contest a KwaZulu-Natal derby with log leaders Maritzburg United at King Zwelithini Stadium on September 12.