With all the votes counted, the alliance of hackers, activists and anarchists had gained a respectable number of seats - 10 - but not enough to take control of Iceland's parliament.
The Pirates and their three left-of-centre coalition partners held a combined 27 seats, five short of a majority in the country's 63-seat parliament.
Of the Pirate Party's allies, the Left-Green movement also picked up 10 seats, the Social Democrats three, and the centrist Bright Future four.
The centre-right Independence party won nearly 30% of the vote and with its coalition partner of the past three years, the Progressive Party, ended on a total of 29 seats.
The Pirate Party's co-founder, Birgitta Jónsdóttir, said the results, which saw them finish third with 14.5% of the vote, were satisfying.
"Our internal predictions showed 10% to 15%, so this is at the top of the range," Jónsdóttir told the Guardian.
"We are a platform for young people, for progressive people who shape and reshape our society. Like Robin Hood - because Robin Hood was a pirate - we want to take the power from the powerful to give it to the people."
Some of the Pirate Party's supporters were less than happy with the results, however. "I'm really sad and I'm really disappointed in our young generation," said Bylgja Gudjonsdóttir, a 22-year-old student. "This is our next generation that is taking the country to the next level. But they keep voting for the criminals we have here."
With 30 female MPs, Iceland has now overtaken Finland and Sweden to become the parliament with the highest proportion of female parliamentarians – more than 47% – in Europe.
The final structure of the government is yet to be established, but the results mean the seven MPs from the newly established Viðreisn or Regeneration party, which split from Independence earlier this year, could hold the balance of power.
The leader of Independence, Bjarni Benediktsson, was confident that his party would be back in power. "I cannot deny that if the results stay this way, it would be natural that we are a leading party in the next government," he told Reuters.
The election was triggered by the resignation of the former prime minister and Progressive party member, Sigmundur Davið Gunnlaugsson, who became the first major casualty of the Panama Papers in April after the leaked legal documents revealed that he and his wife had a vast fortune stashed offshore.