Expedition 51 Commander Peggy Whitson and Flight Engineer Jack Fischer of NASA concluded their spacewalk at 1:21 p.m. EDT.
The pair will move through the Quest airlock to replace an avionics box used for science experiments, while also installing a connector to route data through the alpha magnetic spectrometer.
The first U.S. spacewalk started at 3:45 p.m. EDT on the third orbit when White opened the hatch and used the hand-held manuevering oxygen-jet gun to push himself out of the capsule.
An equipment water leak shortened Friday's spacewalk by two USA astronauts at the International Space Station, but they still managed to replace a faulty electronics box.More news: Donald Trump to host Lavrov at White House on Wednesday
The U.S. space agency made it clear throughout the mission that Fischer's suit was fine and the leak was contained. As a result, NASA officials chose to limit the time spent outside the station to roughly four hours - only enough time to accomplish the primary objective.
This will be the 200th spacewalk at the station for assembly and maintenance, the ninth spacewalk for Whitson and the first for Fischer, who commented, "Test driving my spacesuit for a walk outside on Friday..."
Going into today's spacewalk, Whitson had logged a cumulative 53 hours and 22 minutes of EVA time over eight previous outings, putting her fifth on the list of most experienced spacewalkers and No. 1 among females with EVA experience.
NASA adjusted the normal starting point for a spacewalk - when the astronauts switch their suits to battery power - after a troublesome servicing and cooling umbilical forced forced Whitson to use her spacesuit's internal electrical supply during final spacewalk preps and depressurization of the airlock. He told mission control the Earth looked like a "giant fondue pot bubbling over with awesomesauce".More news: Prince Philip, 95, keeps calm but won't carry on royal duty
The official start time, 9:08 am (1308 GMT), was about two hours after it was supposed to begin, according to NASA.
In light of that, it's pretty fantastic that there haven't been any astronaut or cosmonaut deaths or serious injuries during spacewalks since they began at the station in 1998. However, due to the delay at the beginning of the mission, some of the secondary tasks of the spacewalk might have to be canceled.
The very first spacewalk at the ISS took place on December 7, 1998.
"Oh my gosh, this is handsome", Fischer said as he worked 250 miles above the planet.More news: The Texas Officer Who Fatally Shot Jordan Edwards Is Appealing His Termination