Two major roads out of the port are set to be blocked for four hours on Saturday, the environmentalist group said.
The “No Food on a Dying Planet” action at the Kent port is set to be mirrored across the Channel by other Extinction Rebellion groups.
The Port of Dover said it is aware of the protest and is working with police to minimise disruption.
Five million vehicles and almost 12 million passengers pass through Dover every year, making it one of the busiest ports in Europe.
Chris Atkins, from Extinction Rebellion Dover, said: “As climate change develops, millions of ordinary Britons will face the real and growing threat of food shortages, hunger and starvation.
“Extreme storms and floods are already causing major crop failures across the world, with high temperatures also hitting livestock agriculture.
“This crisis may seem far away now but given the dependency of the UK on food imports we are extremely vulnerable.
“The government must tell the truth and act now.”
The protesters are meeting from 10am, with an Extinction Rebellion spokesman saying the group has assessed that holding the four-hour blockade between 11am and 3pm “will not cause any disruption to vital supplies” such as medicine.
He added: “Extinction Rebellion appreciates the blockade will directly affect ordinary people and businesses, but we feel the action is necessary in order to call the government to action.”
A spokesman for the Port of Dover said: “We are aware of the protest plans and as a result, Port of Dover Police are working closely with Kent Police to ensure as minimal disruption as possible.”