The KwaZulu-Natal are new head coach Sinethemba Badela first signings of the January transfer window, with the former Chippa United boss having replaced Gavin Hunt in December.
Maarman (26) is a former Chippa United player, who has also turned out for Orlando Pirates and Cape Town All Stars, while Mahlangu joined Babina Noko from TS Galaxy.
Both players have struggled for game time under Eric Tinkler at Sekhukhune this season with Maarman playing five times while Mahlangu turned out just once.
A Durban City statement read: "New signings confirmed.
"Durban City FC welcomes Ronaldo Maarman and Siphiwe Mahlangu on loan from Sekhukhune United FC.
“Two experienced wingers. One ambition.”
