One of the Brussels bombers had previously worked at the European Parliament as a cleaner.
An official from the European Union institution said that for a month in both 2009 and 2010, one of the men worked in the parliament as a student summer job.
Although it was not confirmed which of the men involved in the attacks was being referred to, it has been reported that it was Najim Laachraoui, one of the airport bombers.
The man had been employed through a cleaning company, contracted by the European Parliament at the time, a spokesman said.
But he insisted that the man did not have a criminal record at the time as the firm had submitted proof of this to the parliament as required under the terms of their contract.
Brussels was hit by suicide bombings at the airport and on the Metro which killed 32 victims and wounded 270. The attacks were claimed by the Islamic State group.
Briton David Dixon, 50, who was originally from Hartlepool but was living in the Belgian capital, died in the Metro bombing and the Foreign Office said that seven British nationals were injured in the attacks.
European Parliament spokesman Jaume Duch Guillot said: "The European Parliament confirms that seven and six years ago, one of the perpetrators of the Brussels terrorist attacks worked for a period of one month for a cleaning company which was contracted by the European Parliament at the time.
"As a student, he held a summer holiday job cleaning at the Parliament for one month in 2009 and one month in 2010. Those were the only instances he worked at the Parliament.
"As required by the contract, the cleaning firm submitted proof of the absence of a criminal record to the European Parliament."