"We want the good practices applied to Ikea workers in many countries to be implemented all over the world," Alke Boessiger, head of the UNI Global Union which organized the gathering, told AFP.
Even though conditions in many Ikea stores were relatively worker-friendly, she said, in some countries local company managements were preventing workers from joining unions and undermining their rights.
The alliance unites delegates from 20 unions which chose Istanbul to show solidarity with a Turkish union that says it has been trying to sign a collective agreement for Ikea workers since 2010.
Ikea has five stores and 1,700 workers in Turkey, but the staff majority required by Turkish law to bargain for a collective agreement had not been reached, a spokesman for the Turkish Koop-Is labour body told AFP.
"Why we cannot get more workers to sign up is simply the intimidation from the local management, which threatens workers with lack of promotions, harder shifts or even dismissal," said the spokesman, Deniz Akdogan.
The management of the company, Mapa Mobilya (Furnishing House), could not immediately be reached for comment.
The alliance is to publish a report Thursday on Ikea management practices in stores all over the world.