The strike emptied the EU quarter in Brussels, with union leaders claiming that 90% of the officials had stayed away.
A similar one-day action last month saw 13,000 Brussels-based Eurocrats stay away. Some 34,000 people work for the EU across Europe.
Yesterday, a delegation of about 150 trade unionists occupied the lobby of the European commission's headquarters, complaining about a deal struck by Neil Kinnock, the former Labour leader and current commission vice-president, to restructure the pay and conditions of the officials.
Under the changes - due to take effect next year - officials will still be entitled to a pension worth up to 70% of their final salary, but they will have to work longer for it, with the retirement age rising from 60 to 63. Instead of accruing two percentage points for each year at work, they will get 1.9%.
The unions promised more strikes and court action. But the changes will generate savings of up to £50m a year for EU taxpayers, Mr Kinnock claimed. EU governments concluded earlier this year that the current pension system was "excessively generous".
Mr Kinnock said before the strike that he was strongly opposed to it. "Strike action does not assist in the process of obtaining the best working conditions," he said.
According to the EU's pay scale, the salaries of officials start at £16,000 a year, but can rise to £168,000. They are also subject to minimal tax.
