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The €328.6 million ($647 million) fine imposed by European regulators on Guinness Peat Group-owned Coats and six rivals for anti-competitive behaviour on Wednesday is the fourth-largest in European Union history.
The European Competition Commission said the companies ran four illegal cartels, one lasting 21 years.
It said they co-ordinated price increases, fixed minimum prices, allocated customers, shared markets and swapped "commercially important and confidential information" for zips, snaps and rivets and attaching machines used to make clothes.
Coats was fined €122 million while the largest individual fine - €150 million - was imposed on Japan's YKK. That fine was reduced because the company co-operated with the investigation.
The overall fine included a €40 million penalty on Germany's Prym Group which the commission waived because it was the first to blow the whistle.
The EU termed the abuses in the €1 billion European clothing accessories market as "very serious".
Earlier this week a European Court backed a €497 million fine imposed on Microsoft in 2004 for tying new applications to its Windows operating system in a way that harmed consumer choice.
This year the commission has fined an intercontinental cartel of electric power switchgear makers €750.7 million, and also slapped its largest ever fine of €992 million on five elevator makers.
