"Something has gone wrong with the mailing list...it has set off a very messy situation at the city office," said Clas Olsson, acting director of the employment office.
An email call for a recruitment meeting that should have gone out to about 1,000 job-seekers went out to considerably more people, about 61,000 - apparently all the registered job seekers in Stockholm, police said.
Hundreds of people expecting to attend crowded into the alley where the labour office is located and spilled into the adjacent street, a main thoroughfare running through downtown Stockholm.
Emotions were running high and office staff sounded the alarm, bringing police to the scene.
"When we got there it was very crowded and there were some upset feelings," Police Inspector Ulf Lindgren told Reuters.
Olsson told the Aftonbladet newspaper he did not know if the cause was a human or technical error.
Sweden's total unemployment stood at 8.6 percent in January.