The party has broadened its initial platform, which focused on file sharing, censorship and data protection to include other social issues, advocating the Internet as a tool to empower the electorate and engage it in the political — and legislative — process.

“Today’s cadre of politicians is missing out on asking some very relevant questions about the future,” said Rick Falkvinge, founder of the first Pirate Party, which he started in Sweden in 2006. He was celebrating with his German colleagues at Sunday night’s election party in a room filled with disco balls and disassembled mannequins in the Kreuzberg nightclub Ritter Butzke. Thanks to the interactive nature of the Internet, “you don’t have to take these laws being read to you,” he said. “You can stand up, stand tall and write the laws yourself.”

Mr. Falkvinge summed up the significance of the Berlin election for the nascent movement in terms members would understand: “German Pirates have the high score now.”

Sebastian Schneider, who asked to be called Schmiddie “or no one will know who you’re talking about,” a member of the party and one of the people celebrating Sunday night, said that there was no other party he could envision voting for.

“In my opinion, the Greens are a conservative party by now,” Mr. Schneider said. “They were not quite sure if they wanted to join the dark side of the force or not,” by which he said that he meant forming a coalition to govern Berlin with Mrs. Merkel’s Christian Democrats.

There were plenty of young people, many with dreadlocks or beards and a few with both, smoking hand-rolled cigarettes and sipping beer. Others wore jackets with CCC written on the back, short for the Chaos Computer Club, a hackers’ collective that got its start in Berlin and has an overlap in membership with the Pirates. A stand-up comedian working in classic Berlin cabaret style poked fun at the influx of tourists and the recent rent increases that became major issues in the election campaign, saying: “There are no more buildings to occupy. Next we’ll have to start occupying five-star hotels.”

Mayor Klaus Wowereit of Berlin, whose Social Democrats won the most votes on Sunday, assuring him a third term as the city’s mayor, may have paid the young party the highest compliment of all, taking it seriously enough to attack the day after the election. He raised a prickly problem for young men who spend their evenings writing computer code: There were next to no women in their group.