Onyango joined Maritzburg prior to the start of the 2015-16 season and has been a key figure at the back through his first two seasons.
He signed a two year contract when joining and has now been handed a two year extension which is set to keep him in KwaZulu-Natal until at least June 2019.
Club officials have confirmed the latest developments regarding the new deal for Onyango.
Onyango turns 23 in July and arrived at Santos as a teenager five years ago from Tusker FC.
Meanwhile, Bevan Fransman remains under contract with the club for another year.