The three trains cancelled were the 14.13 Paris-London, the 16.31 London-Paris and the 17.04 London-Brussels, the company announced.
Eurostar warns of delays
We are experiencing operational staffing issues in Paris Gare du Nord which we hope will be resolved shortly. However it is likely trains will be delayed throughout today.Eurostar (@Eurostar) 7 juillet 2018
If you no longer wish to travel today, you may change your booking free of charge: https://t.co/H8qNeyQgBC
Three Paris-London trains - the 11.13, 12.13 and 13.13 - were delayed for about two hours, according to French rail company SNCF.
In a tweet Eurostar said the disruption was due to "operational staffing issues in Paris Gare du Nord", adding that it hoped they would be resolved shortly.
A spokesperson told the AFP news agency early on Saturday afternoon that the problems had been resolved and the cancellations were made to "allow traffic to return to normal".
The service suffered delays on Friday because of an electrical fault.
The disruption comes at the start of French schools' summer holidays with roads clogged with traffic jams and a strike on French national railways.
The weather's fine, though.