The France-bound Eurotunnel train stopped about a quarter of a way through the tunnel at around 7:30am in the morning after a problem with an overhead power line.
The 382 passengers and four dogs on board were evacuated after 20 minutes via service tunnels to the French terminal as it was expected to be some time before the train could be moved.
A Eurotunnel spokesperson advised people who did not need to travel on Monday to go on another day as queues were building up.
Delays have been expected throughout the day.
High-speed passenger train service Eurostar also said it had cancelled four services on Monday and had seen delays on its services.
Eurostar told customers, "If travel today is non-essential you can exchange your ticket, free of charge, to another available service within the next four months."