NASA astronauts Nick Hague and Christina Koch floated outside, a week after the first spacewalk to install new and stronger batteries for the station’s solar power grid.
Ms Koch was supposed to go out with Anne McClain, but there weren’t enough medium suits readily available, so the first all-female spacewalk had to be scrapped.
A third spacewalk is planned for April 8, but that will also be mixed gender.
The space station’s outdated nickel-hydrogen batteries are being replaced with lithium-ion batteries.
The new batteries store power collected by the solar wings and keep the outpost running when it is on the night side of Earth.
Mr Hague and Ms Koch arrived at the space station two weeks ago.