"Today's exhilarating #spacewalk will be etched in my memory forever -- quite an incredible feeling! " Peake tweeted.
Peake, 43, was accompanied by U.S. astronaut Tim Kopra on the extravehicular activity (EVA) to replace a failed power regulator, install a valve and attach cables outside of the station, according to the space agency.
The ESA live-tweeted the spacewalk with a blow-by-blow description of the astronaut's moving along the station's truss, unbolting the failed regulator and installing its replacement.
The spacewalk had been expected to last about six hours, but had to be cut short due to a "a small amount of water" in Kopra's helmet, NASA tweeted.
Peake and Kopra were back inside the pressurized space station at 12:31 p.m. ET, NASA said.
This is at least the fourth time an astronaut on a spacewalk has found water inside his or her helmet or suit.
On March 1, about 15 milliliters of water were found inside astronaut Terry Virts' helmet after a seven-hour space walk. Virts said he'd noticed traces of water and dampness a few days earlier.
NASA previously said the suit worn by Virts has a history of "sublimator water carryover." Water in the sublimator cooling component can condense when the suit is repressurized after a spacewalk, causing a small amount of water to push into the helmet, NASA said.
In July 2013, between 1 and 1.5 liters of water backed up in the suit and helmet worn by Luca Parmitano, prompting fears he could drown in his own helmet. The spacewalk was cut short, and NASA implemented changes to its suits, including the addition of absorbent padding in helmets.
On December 24, 2013, water intruded into the helmet of an astronaut during a spacewalk. NASA commentator Rob Navias said it was noticed during the repressurization of the crew lock, the area from which astronauts enter and exit ISS while in space.
While Peake became the first astronaut to walk in space as a British astronaut, Michael Foale -- a dual U.S. and British citizen -- was the first person born in Britain to walk in space in 1995.
Foale, however, was an astronaut for NASA, not the European program.