A Eurostar train coming from England was able to enter the tunnel just after 8am local time on Saturday, a Eurotunnel spokeswoman says.
Full services were expected to resume gradually.
The tunnel had been closed shortly after midnight when a crowd of migrants stormed the entrance near the northern port city of Calais.
At the time, a firefighter at the scene said 10 people, including seven migrants, suffered minor injuries during the incident.
The interior ministers of France and Britain signed an agreement in August to set up a new "command and control centre" to tackle smuggling gangs in Calais, as Europe grapples with its biggest migration crisis since World War II.
Thousands of people from Africa, the Middle East and Asia are camped in Calais in slum-like conditions, and at least 13 have died since June 26 trying to cross into Britain, where many have family and work is thought to be easier to find.

