The foray, the second spacewalk in two months and relayed on state television, is part of China's heavily promoted space programme which has already seen the nation land a rover on Mars and send probes to the moon.
In June, three crew arrived at the station, where they are set to remain in space for a total of three months in China's longest crewed mission to date.
On Friday, astronauts Nie Haisheng and Liu Boming successfully exited the Tianhe core module to install foot stops and a workbench on the station's robotic arm, said the China Manned Space Agency in a statement.
Video footage showed the astronauts working outside the spacecraft while tethered to it with a long rope.