Activists say the deals will hand more power to multinational corporations which would lower food, environmental and labour standards.
Unions, environmental groups and consumer activists have taken to the streets of Brussels.
It's a groundswell that protesters, like Greenpeace spokesman Mark Brady, hope will persuade the EU to reject two major trade deals.
"We are against these trade deals because they are a threat for the environment, for health, for labour regulations, and they give so much power to multinational corporations. We need to protect the public interest, even if in some cases it means that it limits trade."
The first is the Transatlantic Trade and Investment Partnership, or TTIP.
While it's still being negotiated in secret between Europe and the United States, its ultimate aim is to create the world's biggest free trade zone.
The EU says TTIP will boost its economy by around $180 billion by creating millions of jobs dependent on exports.
And by cutting cross-border trade levies, the EU says consumers would also enjoy cheaper products and services.
But as Kurt Huebner, from the Institute for European Studies at the University of British Columbia, explains there are still many areas of contention, including how government agencies should operate and attitudes about food safety.
"There are different philosophies to things like genetically modified food. On one side we see a situation in Europe where not only damage needs to be caused in order to intervene, but in the European case, producers have to showcase that a product or services are safe for consumers. It's exactly the opposite attitude with the United States of America."
A second trade deal struck between the EU and Canada is similar, but smaller.
The Comprehensive Economic Trade Agreement, or CETA, could be signed as early as next month and brought into effect next year.
Luisa Santos, a member of the TTIP Advisory Board, insists both deals will change lives for the better.
"CETA is not going to impose us to eat hormone beef or hormone chicken or chlorinated chicken, or these kind of things. So we will be able to continue to eat the products we eat in Europe. We will have access to new products, of course and we will have access to new services, but I think that's a good thing. That's part of evolution, that's part of innovation."
Both agreements will be the focus of a meeting in Slovakia later this week between Europe's trade ministers.
While there is wide support for CETA, some countries claim it has many of the same problems as TTIP.
One of the biggest critics, Austria, is worried multinational companies will be able to challenge government policies if they feel regulations put them at a disadvantage.
Until now French and German politicians say TTIP talks have either failed or should be suspended.
The University of British Columbia's Kurt Huebner isn't confident it will be approved.
"I don't think Obama has the power in his last couple of months to push through a deal. There's too much opposition in the US as well. It will be necessary for a new start after November, and a new start would have to include a total kind of new thinking about comprehensive trade agreements that take up a lot of valuable critique positions from various corners of national politics."
