As of November 2019[update], PSI has 700 affiliated trade unions from 154 countries representing over 30 million workers.

[1] In March 1907, the executive of the German Union of Municipal and State Workers, based in Berlin, issued a call to "workers employed in municipal and state undertakings, in power stations, in gas and waterworks, in all countries" to attend an international conference in August 1907, in Stuttgart.

Four Danes, two Dutchmen, eight Germans, a Hungarian, a Swede, and a Swiss met in the Stuttgart trade union building for the First Congress of Public Services International, representing 44,479 workers,[2] and they founded the International Secretariat of the Workers in Public Services.

This grew rapidly, and by 1913 represented more than 100,000 workers, enabling a part-time salary to be paid to the secretary, based in Berlin.

[4] PSI's pro-worker stance has put it at odds with the WTO, World Bank, and IMF who predominantly promote market solutions.